Struggle Is Real.

I've been dating this dude for about four months now and I really love him. He's so sweet and supportive and asked for nudes once and when I said no he never asked for them again. Constantly complimenting me, and I feel like he's always putting me first. But, the thing is is that we met online and I've only seen one picture of him. I don't know if the him online is who he is in the real life, and I don't know if he's faithful or if I'm just being paranoid. I really need some advice