Sorry if this is fairly long, I'm just hopeless

Hello everyone. I'm looking for some guidance. I've been with a girl for over 7 months. We have been problems for some time now Actually it's been nearly 1 month. I was stopping smoking and starting a new job and I was quite heavilly stressed. I came out as being agressive and even mean sometimes. Well, that was a hard time but we worked hard at getting over it. she says, it was especially hard for her and everytime a little thing happened she'd get upset more easily because of accumulation of bad discussions or arguing, etc.

The problem there seem to be a distance between her and me. I'm feeling on the defensive because I feel like she's lying to me and a reason why she is distant is because she's cheating or wanting out or something.

Monday 9h15am, I called her up from work several times for 3 hours to wake her up for her to do her school assignment. Well, she calls me up at 2h30 pm and says she's been took a walk from 10am to 2pm in the forest. THis is extremely weird considering the fact my girlfriend doesn't do any physical activity let alone walk for 4 hours). She got defensive when I asked her about it and told her I still tried to call several times from 9 to 10. She says she couldn't explain why she didn't hear it but she mentionned she was sleeping (she has trouble hearing the phone when sleeping) and the phone isn't in the room but in the hall. Yeah ok...

Today, I do the same because she has to get to school. SO i called her up for over an hour and it was busy. Nobody's ther but her so I'm assuming it's her. she calls me up 10 minuts later (after I called for an hour and it rang busy) and says she was sleeping and she JUST woke up so she couldn't possibly have been on the phone. Well what the hell was that busy line for over an hour then.... she says: I really don't know.

There, you have 2 examples this week and a lot more weird things like this have happened for awhile now. I have the feeling she lies to me a lot (confront her about it and I get nothing), I'm feeling her distant (she says it's because of the accumulation of problems and me saboting the relationship by not trusting her more). A month ago she bought new clothes, she'S fixing her hair which she was never doing before and has a sudden interest in physical activity.

I'll be the first to admit I'm a very paranoid person and I've been cheated on before by a girl that I gave everything to. But sometimes when a feeling is this strong I'm right. Plus, this is the first time I'm feeling this since we are going out. I'm scared because if this fear, paranoia, distrust whatever would go away; I'd suspect we woudl be happy. But hey I can't make the feeling go away nor ignore weird facts.

I'm really lost, depressed, all the works. I really need advice I'd really appreciate it.