I feel for you my friend... you sound very sad and confused about it all.
I would like to propose a solution to you. Take what you can from it and leave the rest... I hope it is somewhat useful.
First of all I think it is good that your man is not pursuing this woman at the moment as I think there is a lot of relationship building that you both need to do together. I don't know what his story is, so I will just go on what you have said and leave it at that. Perhaps he can add for himself what will work or not work for him.
I think the first thing to do is to stop looking at yourself in terms of what people have said and done to you in the past. That was the past and you are not there today. Your concern is who you want to be in the future. What it sounds like you want to be is confident, self respecting, have feelings of self worth and feel as if you are attractive both physically and sexually as much as for your character.
How to do this? Well you could do that in a number of ways; stop looking in the mirror and putting on the makeup you have started to put on may help. I find with make up that some women hide themselves behind it and some use it to enhance. I can guess immediately why a woman is wearing makeup and the latter to me just makes a woman look worse. Of course it is just a guess though
By not looking in the mirror I wonder if you could start looking inward and really become aware of your body and your inner beauty. I know it's there, I can sense it in your posts. You have a way of writing that is gentle and lovely to me and I wonder if you can find that somehow and really embrace it.
The physical activity you are doing will be useful I think in terms of making your adrenaline run and also exercise offers time for one to go inward as a lot of it is repetitive and boring if you don't have something to think about. Good for you for starting that.... I hope though that you can focus on it as a tool to develop your feelings of happiness, well being and good body sense rather than to make yourself look better as I think in the long run that would be healthier.
Spending time writing about what it is you love about you, writing about what you would like to achieve (remember to not get overwhelmed by it... perhaps breaking it down into now, later and the future will help), reading some books on raising self esteem (Nerdist has read many! He has a whole list that is very useful... some of which are on the book list), doing art if you are creative, singing if you like to sing, petting an animal if you like that, anything that you can feel your own personal energy running through is helpful... talking to a therapist is a good idea too.
The point is that your husband did not necessarily go out and fall in love with someone else because he doesn't love you. He did not go out to find someone to compare to you...but it has triggered that in you it seems.. you are unique and special in his eyes, it sounds like and he loves you, otherwise he would not be feelings so bad about all this... I don't think he is trying to make you feel guilty, if he is then that is another story and you can come back and tell us, but wants you to know his feelings...if you go out and start focusing on bettering your situation then he will feel that he did the right thing telling you his feelings. The last thing you want him to feel is that he shouldn't of said anything. That will close down communication and eventually he will go outside of your relationship without you knowing because he doesn't want to hurt you. I say all this in terms of what I would do and from my experience. If I were you I would thank him for this experience and tell him how you are going to make changes in your life for the better because of it.
I do not find myself as an overly attractive woman physically but I have built my confidence up and know that is attractive to some and certainly attractive to ME. A few years ago I was not confident and the way I was treated and over looked hurt me greatly. I worked hard on myself and FOR MYSELF and now I get a lot of attention and am able to give a lot back.
Good luck and big hugs to you...