Think she cheated

And snoop in her phone.

Yeah, this relationship's got a kick-bun awesome foundation.

If it were me, I'd end it. She's the one that should end it...because you don't trust her and you're a nasty snoop. Also she can't make up her mind who's her b/f.

Let's see: you snooped on her phone. That means you don't trust her and you're suspicious of her behavior after one month. If you're doing that sort of behavior then you have no chance of a future relationship.

Then there's that fish story she gave you. Why couldn't she just tell this guy on the phone that it is over? Don't believe everything you hear ... even if you want to believe it. For example, hypothetically, let's say it's a month from now and she becomes pregnant? What are you going believe?

"my question is should i believe her or not?"

Time will tell.

My question to you is why you hooked up with a girl who clearly is not over her ex? You moved WAY too fast. She had too much baggage. She should not have gotten involved with anyone so soon.

What does SHE say about the future? How is she acting NOW?

That guy gives your girl hard sexual satisfaction, it is like drugs. Your girl depends on sex with that guy physically. I don't pretend to be truth, it is just my IMHO.

If she is hot in the sack...stick it out as long as possible for the sex.

If you are looking for a long-term relationship...first grow up and then look for someone else.