Should I trust my boyfriend?

I have been dating my boyfriend for 9 months now, and for these 9 months, it has been near perfect. Before we started dating, we were the BEST of friends, so we kinda carried that on to the relationship, the kind where you can act like a total idiot with them and be goofy, but still be totally in love. We always tell each other how we're exactly what we've been looking for in a partner; looks, personality, everything. He constantly looks at me as if in amazement and tells me he's the luckiest guy in the world and is so shocked and happy that I'm all his. Like he's seriously swooning over me. But just this month, we had a huge fight that ended in him asking for a break. Now granted, the break only lasted one weekend (there was no date set for the end of the break, he said it would last until he sorted out his feelings. I was terribly distraught the whole weekend cause he said he would decide whether or not he wanted to leave me over the break), but the reasons for the break were all faults he found in the relationship, and pretty much in me. But when the break ended, he said he made a terrible mistake and said leaving me would have been the stupidest thing he's ever done in his life. He said he regretted asking me to leave during the fight the second I left his house and he missed me the whole weekend (still sorting feelings though). Basically, he said I had made him mad and he didn't know what he was thinking when he said he wanted to break up, that everything could go back to normal now and that he still loved me just as much as he always has. Now the reason I upset him is cause I have clinic depression and I'm a very paranoid person and was always paranoid he would cheat or leave me. I was previously in a relationship where my ex had been texting and Myspacing dirty, naughty things and calling another girl "boo" and whatnot while we were dating and I found the messages. He never admitted if it was more than just dirty messages. I've had terrible trust issues since and I can't ever seem to get past that terrible pain... I'm the type of girl who will give her all to the one she loves, so when my ex did that, I was totally and completely crushed. My heart was mentally leveled to the ground. Now my current boyfriend says he could never get any better because I'm the best and most wonderful looking girl ever and swears he's the most faithful guy ever and that I'm all he ever wants, but I have a hard time trusting that. Ever since the break, he hasn't been texting me as much, and he's been texting his absolutely GOREGOUS female friend like ALL THE TIME. And he still invites me to hang out A LOT, but theres like days that he does stuff and doesnt talk to me at all and pretty much disappears off the face of the Earth. Him and the girl he always texts seem very close and he's the shoulder she always cries on. I don't like that. Especially cause hes admitted to having feelings for her a while back but apparently not anymore cause he has me. They go to the same school so they have plenty of time where I dont know how they interact. He always sends little hearts and wink emoticons to her when they talk, they talk very cutesy with each other, and if she doesn't reply he always is like "Hello? Are you there? Hello?" and vise versa. And they text late into the night... When I bring up how much they talk and how the texts sound bad, he gets really sad/upset and he says "She's just my friend, you're my one and only. I really wish youd believe that." but I still can't handle it. And of course there's this factor: she has a boyfriend, but that didn't stop my boyfriend from luring me away from my previous relationship (the one with my terrible ex). She's very unhappy with her boyfriend at the moment so I'm worried she might be falling for my boyfriend since he's her source of comfort. Now, he has never given me a reason to not trust him. He's the best boyfriend I've ever had and I feel like the luckiest in the world.... I'm just worried I'll loose him. I want to stop being this way, being paranoid is no fun. And half of me even thinks I'm worried for nothing, but I can't get past this feeling. I want to believe it's all ok and that I'm looking at this all wrong cause then we could both be happy. He always promises that everything will be alright. Should I worry? Or is everything really ok like he promises?