I'm 21 and can't get/keep an erection

[you_know_my_name]

I'm 21 years old and I've been having trouble getting and keeping an erection. I broke up with my girlfriend about 4 months ago and ever since then I've been having trouble. My ex and I were together for almost two years and she was the only girl I've ever had sex with. About a month after we broke up I started seeing another girl and whenever we started messing around I would only ever get half hard, even if she was giving me a blowjob. After things with her didn't work out I didn't try to do any sexual stuff with anyone because of what happened. I've just started seeing a new girl that I've known for a while. She's very attractive and I like her a lot but for some reason I can't keep an erection with her. I can have a full erection and if she goes to give me a blowjob I go soft again. We haven't tried having sex yet so I don't know how that will go, but I'm nervous that the same thing will happen. I also don't get erections as much as I used to.
I don't want this girl to feel like she's not attractive and I don't want this to be a problem anymore. I've talked to her about the problem and she says she understands, but I want to be able to have a normal sex life. What should I do?

[Nobody7]

Are you watching porn? You may have porn induced erectile dysfunction.

[YardBull]

Since you were with your ex-girlfriend "for almost two years" and it's fairly recently that you broke up, give yourself time to become more comfortable with these new relationships.  Take intercourse off the table and stick with manual or oral methods of intimacy.  Thankfully, you have an understanding current girlfriend, so there is no hurry.

[you_know_my_name]

These problems are happening with manual and oral sex as well

[YardBull]

Hmmmm . . . .  It just may take time.