Couples Forum: Who Is My Baby's Father?

I recently had my son who is 6 months old but I’m not sure who the father is. The guy that I thought is the dad left me since he found out I was pregnant and hasn’t come around,not even to see his alleged son.
The other guy was an ex that now wants to do a DNA test on my son to see if he is the father because of some certain features they shared and he seems to be interested in him and wants to be a part of his life if he is the father.
The problem is that he was unfaithful to me in the past (we were engaged for less than a year and he broke the engagement only to find out he had impregnated another woman)
I can’t trust him again…..do you think it wise for me get back with him (if he is the father ) and to work at developing a relationship and being a family for my son’s sake