I(20M)have been with my girlfriend (20F)for about three months now. It's both of ours first relationship and first time having sex. While i don't really feel stressed or anything,i just can't turn my brain of and enjoy the experience. When she's performing oral sex on me I hardly feel anything other than the sensation of touch. Not bad , not good just neutral. Most times we can't achieve penetration because once i start going for it i struggle to maintain an erection. I can get her to climax using my fingers and simultaneously stimulating other areas of her body but there's really not much feeling when she tries to do the same. It's important to mention that I've never had a problem getting off on my own. Any advice?