Hi Aurelie, I've lurked on this forum for a while now but have never posted until now. I'm also from London and a few years ago i found myself in a very similar position to what you find yourself in now and I wanted to give you some advice.
First off, To answer your question, yes you can overcome your boyfriends jealousy and keep both him and your lover. I have done this with my husband, it's not a given though.
It sounds like you want to continue with your poly relationship but your boyfriend isnt so keen. As its something you want, YOU need to be the one who takes responsibility for it and you need to be the one to make it happen.
So your boyfriend is messing things up for you by being jealous and asking questions about how he measures up sexually with your lover. Questions that make you feel quilty, and that you dont know how to answer You can do one of two things.
A. Allow the current situation to continue by avoiding the issue and therefore allowing it to fester and get worse.....Or
B. Take positive steps. You need to nip these questions in the bud. Short term pain for long time gain.
Reading between the lines and without getting to graphic about it, your situation is this.
Your boyfriend is the gentle, sensitive, loving type and this is how he acts in bed. You say he is good looking and in great shape and you say your sex life is good and that he is considerate to your needs. So this means that you are sexually attracted to him and he does turn you on and he does make sure you get off. It sounds to me like you have a good sex life with your boyfriend, but also, the harsh truth is that he does not and cannot satisfy you sexually, not fully.
You say your lover is very well endowed (Twice the size of your boyfriends) and has amazing self control (He lasts much longer then your boyfriend) Sex with him is very exciting and there is nothing that we haven't tried.(He is much more adventurous than your boyfriend) You very rarely go out (He can make love to you all night, multiple times & your boyfriend cant) He makes you have orgasms in a way that your boyfriend cannot and never will. (Your orgasms are much more intense with him and he gives you a lot more of them than your boyfriend can, and he can do this because of his size, staying power and natural god given talents as a stud, talents that your boyfriend does not have and cannnot acquire or be taught by you or anyone else) Am i correct with these assumptions?
O.K, lets address the penis issue first. Your boyfriend is small/average and your lover is huge? Your boyfriend keeps asking if your lover is bigger than him, and you dont know how to answer him! If he asks again, I would suggest that you tell him the truth. Theres no need to tell him your lovers penis is twice the size, just tell him that, yes, he does have a big dick. I think he knows this already, simply because you refuse to answer the question. Once you answer him he wont need to ask again. It's not the end of the world and he will get over it.
Your boyfriend wants to know how he measures up in bed when compared to your lover. As advised by others I think you should try the 'Your different, and I enjoy you both' approach first.
They sound like polar opposites to me, point this out to your boyfriend and tell him that you enjoy them both, but for the opposite reasons. Tell him thats why you need them both, and remind him that you told him that you needed your lover from the beginning.
He may not settle for this, he might want a simple, who do you prefer in bed, me or him? My husband wanted to know this. If your boyfriend wants the same, I suggest that, again, you tell him the truth. He will be hurt (My husband was) but, again, it's not the end of the world and he will get over it. (My husband did)
It will put an end to your current situation, and the two of you can rebuild, and decide what to do from there.
You also say that you love them both. Lets put sex to one side for a minute. It's important, but it's not everything. Reading your posts you say this about the two men in your life.
Easy to be with.
A great Dad.
I love him in spite of myself.
I dont like him that much
Other than sex, we dont have much going for us.
Aurelie, it sounds to me that you love your boyfriend a whole lot more, and I've got to say, by your description of him, he does sound special, a real keeper. You say that he has shown both you and your son great kindness and that he looks after you both and that he is very demonstative and affectionate to you and your boy. You say he comes first, and so he should. It's not just about the love you share together, but also the love that your son shares with him.
Tell your boyfriend that he comes first, tell him you love him more and keep telling him until he knows it and feels it. Return his affection and reassure him with your words and actions and then reassure him again. I promise you, his jealousy is about more than just sex. Make sure that he knows that you, him and your son are a family, and that your lover or nothing else will ever change that.
You say he has a sex drive that matches your own, make sure you dont neglect him and he never goes without the sex and love that he needs.
I hope that you can keep your lovely boyfriend and that your love blossoms and that your son continues to get the great Father he has now. I also hope that you can keep your lover and that he continues to give you the sexual satisfaction you deserve.
I have done just that, and you can also.