Any difficulty to sex w/ 4”?

Me and my girlfriend have been together for sometime now and both have been wanting to try sex, it just didn’t happen during our school year so the plan was to try sometime when we both went back in August. It’s always been a concern of mine that my size wouldn’t make it possible, or difficult in some way. And i don’t mean acceptance-wise, we would be each other’s firsts and shes had her hands on my penis before and was fine with it then. I’m kind of overweight, and she’s a bit smaller than me. If any of you out there with more experience than me would be able to impart some knowledge that would be great. thank y’all