I'm new here too and on the other side of the fence in that I'm looking for advice on how to broach the subject of poly with my mono husband....
Just thought I'd say a couple of things though..... I can relate to your insecurity and self-esteem issues... my husband also has very, very low self-esteem. He became very dependent on me in recent years (he had crippling panic attacks) and this really reduced my respect for him. I believe (and it's far easier said than done) that we need to like, love and respect ourselves before we can expect others to do so....and I really struggled with that concept myself, having deep issues of "I'm not good enough / I'm a bad person" etc. etc. which were rooted in childhood. Through having some therapy, I've learnt that low self-esteem is a really, really big waste of time... we're all imperfect, we're all struggling one way or another! Just because we put on a bit of weight / let ourselves get unfit / do whatever, doesn't make us bad people, maybe just insecure and unfulfilled for whatever reasons.... but we might as well like ourselves because confidence and ease in oneself makes us so much more likeable to others... there are lots of easy things you can do to increase your self-esteem, I did a few exercises myself and they really helped. Have you tried writing down 50 things you like about yourself? At first I thought.... 50?! I can't think of 50?! But I stopped myself at 53.... (and I'm not a big-head, just the opposite).
Secondly - in what you've written, and the fact that you've taken a step to come onto this forum and to be proactive about talking about this and finding out more.... you've just proved to yourself that you're taking control of some of this... and IMHO you should applaud yourself for that. It takes guts.
Third thing is, you mentioned being on a waiting list for a counsellor. Have you ever considered online counselling? I reached a terrible low point a few months ago and found a most amazing online therapist (I talked to her once a week by skype, she also does email sessions) - if you'd like me to put you in touch with her, send me a private message. (She's based in England and I can honestly say my sessions with her had a huge, positive impact on me.)
42 isn't too late. I'm 41 and just started dealing with my "stuff" last year.... it's never too late to tackle whatever you want to tackle.
Good luck and good on you for taking the first steps.
The day came when the risk to remain tight in a bud was more painful than the risk it took to blossom.
~ Anais Nin