I am in sort of a messy situation I need some advice on. I've been living with my gf for past two years. I'm working while she's in college which is paid for by her family. So she's home most of the time.
One of my best friends from Nepal was coming to the US too so I offerred him a place to stay while he gets familiar with the system, and now everyday I am in awkward position because my friend and gf are in the house all day while I work. I am not sure what's going on with them but they seem to have gotten along a lot and they do a lot of things together while I am gone at work. I don't want to ask anything because of the circumstance so I have been acting like nothing is in my head but I am getting a big headache.
Any suggestions on what to do?

Let them read sajha :)

 Put a hidden camera u will find out the truth, if caught on camera post their sex video on pornhub n mess up their life, else call the program cheaters, they will do it for u, or call Jerry Springer. Trust me bud, your gf is sexing with your homeboy, i used to screw my frens wife so...its obvious when you leave opposite sex together in a same room or apt. Opposite poles attract each other.

After adding your contribution to the great Mastishare collection, you should look for a new place at a very very inconvenient area for your जार so that he won't follow you like a shadow. See if your gf of two years still has stomach-butterflies left for you. If she does, she will follow you.

Tell her to get a job...like russel peters said....Ferrari with no engine....sits there and cost me money...

Nowadays, I notice girls hang out with non-working, hippi type of boys. They don't care about hard working, family oriented and intelligent guys. 

He also gave free fun u know, gals don't care till 25 after they hookup with those so called hardworking intelligent guy. It's hard to tell who is intelligent .

Reminds me of this under the couch. LOL.

By chance your girlfriend and friend might read this and start "doing it" to get back to you.

You are so lucky you have a GF, who loves you, I will think even if she is messing around and still loves you . Thats it. That's all it matters. 

How often u used to have sex with your gf when your best fren was not with u?Don't tell me u never had sex with her.If she feels less interested to you compare to past then there is something goin on.
Don't feel too much insecure.If she truly loves u then u don need to worry but if u both are in [Disallowed String for - Bad word 'fuk']a [Disallowed String for - Bad word 'fuk']a relationship screw her and find new one.