My boyfriend is possibly cheating, what do i do?

Hi ladies, I’m not a mother but I could use a lot of advice right now. Last night I couldn’t sleep and I never get on my SO’s phone, but i decided to last night. Gut intuition maybe? To give some insight, we’ve been together going on 5 years in a few weeks and we’ve lived with his parents for 2 years, but just got an apartment about a month ago. We have a good relationship and it can be rough, but we move past it. We both have snapchat, but for some reason we’re not added on each other’s accounts. However, a girl with the same name as mine is added on his. I kept telling myself that it wasn’t what I thought it was because maybe he thought it was my account, but our profile bitmoji things are completely different so that can’t be the case. I did some digging and they deleted the conversation between them. The girl is single, and me being the desperate person I am, added her on my account. Ladies PLEASE give me the advice I need to hear before I do something stupid. I want to message her, but i don’t know if that’s the best decision. I’ve been down about it all day, and I know I won’t be able to sleep without knowing something and I’m gonna force myself to look at his phone again. Please tell me what to do.

First ask yourself why you have the suspicion? Has his behaviour, attitude, routine changed?
Are there unresolved issues that make you feel insecure and vulnerable?
First thing is to understand why you feel this way and decide how you want to approach it.
Do you need to resolve things inside yourself in order to feel able to communicate with him more effectively?
Communicate your feelings with him and try to openly discuss the issues.
The worst outcome…well, 1 - you break up and move forward apart or 2 - you stay together never addressing things and your relationship deteriorates and breaks up.
The best outcome - you increase communication and understanding and work through things