Will this go on forever?

When my sweetheart and I started seeing each other, I knew that he had had a very painful breakup with a woman he had been seeing for 8 years.( This woman is also the mother of his only child) I confirmed the things he told me about her like that she is very selfish and likes to hurt anyone she is in contact with...on
purpose. She cheated on him constantly and had abortions whenever she got pregnant, and whether or not they were his, God only knows. In general, she was just a very hurtful woman that lied and cheated. Like I said, I have confirmed what he told me through people that know both him and her. As a result of this relationship with her, he has the misconception that all women lie, cheat, and can tell him nothing is going on.....with a straight face. He has made comments to me that he worries when I go to work that guys are hitting on me, and that he hopes i'm not cheating on him. I tell him that not all women are like his ex and don't lump us all into the same group as her. I also tell him that only time will heal the wounds in his heart and I do my best to be patient. Sometimes, though, I am really hurt by the insinuation that I would even consider cheating on him. We tell each other all the time " I love you" and for the first time in MY life, I can say it and really mean it.
My question to you is: Is it true that time heals all wounds or is this insecurity something that lasts forever?
I would love to hear a guy's opinion on this too