Depressed and hopeless

No, you are not right. Plenty of people are that age and older without having had a long term relationship and they are not depressed about it. They just live their lives and whatever happens does just that. SOme are just workaholics and don't notice at all.

Who looks after your son? If it's the woman who had the baby then maybe you see she has a partner and that makes you want it. Just guessing.

If you don't think the Zoloft is helping, then it isn't. Talk to your doctor about that and either agree on a higher dose or a new med. No point taking one that does nothing is there?

You should be aware also that many meds take away our interest in sex and our ability to perform, as males. Which in turn inhibits our chances of finding a partner.

My suggestion to you is to stop looking for a partner right now and concentrate on your depression. Get that sorted and then look again. I have to say the times I searched for partners I never found one. The ones I have been with just arrived, circumstances brought us together. I currently have had a 19 year relationship with the lady who is the mother of my 2 children. I have two others as well. This relationship will last. I'm very lucky she has stuick by me through some very bad times.