Yes I think you can attribute most of your relationship problems with women from your mom's death but you can get help. Are you married now?
My dad died when I was 2yrs. from stomach cancer and the only memory I have is when they removed him by ambulance from the house. In those days there wsn't grief counselling for kids, like now.
There are very important bonds that are made when we're children and yours was broken therefore you grew up not being able to trust enough or not expect any lasting relationships. I really think you should consider therapy to explore this, so you can have happier relationships.
I also volunteer in the Q & A section of this website and I wanted to caution you about watching porn. We've had several young men complaining about sexual dysfuction because they're watching too much porn. It's possible to become desensitized and loose the ability to become stimulated by regular sex with a partner. Think back to the frist time you saw porn and how easily excited you got. If you were to go back and watch what you watched the first time - I bet it wouldn't do a thing for you. I read several cases where young men suffer from ED because they can't perform with their partners anymore. I just wanted to let you know that this can happen. I don't think that most people know the real danger it has on their sexuality.
Best of luck to you.