Just really need some advice...

I've been in my current relationship for 2 years now, and ill tell you it hasnt been the easiest ride. But most days i fell like it's well worth it! To give a little background, this is his first, long term relationship. Me on the other hand, was previously in a 6 year relationship.

Thing have been rough these past couple of months. Back in November i moved to his home town to be closer to his family,(been leaving with his parents this whole time)and honestly it has been a lot harder than i thought it be. I have no friends or family here and feel lonley sometimes. That has caused us to arugue more than we ever have. To cut to the chase now, this past Sunday i found a message on facebook from his best friends sister. They had seen each other that morning while i was at work. The message i read was about her apologizing for having bad breath, and about how she wished the kiss was longer. I flipped out! I asked him what happened, while i see him shaking holding his phone. He says she had kissed him on the cheeck and that was all. I really don't know if i believe him, cuz as im going through his email at that point i saw they were talking that morning, even though those messages werent on facebook anymore. So obviously he had deleted them. He denied it, and when i showed him he said he forgot. I talked to that girl n told her this was very disrespectful and that i dont want to have to deal with this so she needed to keep her distance, or we would have problems. Ive gotten close with her brother and i know she has a husband and a baby and im not one to break up a family and cause drama.(But believe me, i have no issue with it if she continues taking to him). We settled it and he promised there was nothing else i needed to know. I told him i was gone if i find out he is lying again. So its been hard these past few days cuz i cant shake that feeling. This morning we had another arguement about the car breaking down, so i left in my car to cool down. When i got back home he sat next to me n told me he loved me. I told him i wanted to talk about it, cuz thats how i feel we can solve it, while he would just like to drop it. He went back to what he was doing and idk i just feel so alone right now. Idk if im making the right decision. I cant imagine my life without him and he says the same thing, but i dont want it to be six years down the line and realize this isnt gonna work out. I just needed to get this off my chest and really just need someone to talk to about this. Any words or advise would be appreciated!