I need advice for my reationship, I am ruining it

I have been seeing a man for 8 months who is 15 years older than me (I am in my early 20’s and he is in his late 30’s) despite our age gap we get along well and the age gap is not really where our biggest problem lies. I am a very sensitive and emotional person by nature caring and loving and my worst trait is probably the fact that I am insecure due to my low self esteem where as he is the one who is more strong emotionally and “cold” as he would say, he is more affectionate than caring but shows me in his own way that he does care, just not as much as I would have liked (or as much as I would need). My last relationship ended very badly over two years ago and I thought that I have worked through all the things that causes me to be insecure but now I realize that I have not. I am constantly thinking he is hiding things or other women from me(although he has never broken a promise that I know of or given me a reason not to trust him) but I constantly look for things, constantly thinking he is just using me because I am not good enough for any man because I don’t have anything to offer. I suffer from depression and have started taking medication again about 2 weeks ago and was booked off for 3 days, I have not been honest with him, he does not know that I have this condition and I told him I was on leave for 3 days.I did that because I don’t want to add anymore drama although I know he won't push me aside, or that is what I choose to believe. I know that the problem is with me and that I will lose him due to my own actions. I don’t know what to do anymore, but I do know that I want to give our relationship a fair chance and that is not what I am doing.I want to trust him and feel secure in our relationship and not cling to the past anymore as he is nothing like the previous guy.