Since the last time I posted here (about a month ago) about my fetishes and one concern with that was letting my future GF know about them, well, I have found someone out of the blue since then

And even better, I've told her about all of my fetishes and she incorporates them into our play time! Which makes me ecstatic!
But the problem I'm discovering is that I'm so use to being by myself and working with my fetishes that I don't really function sexually without them. The past few weeks we've been having regular sex, she's enjoys it but the problem is I'm unable to cum from it. We can only do missionary (I've suggested her being on top but she doesn't want to because she's a bigger girl and it's hard for her) as she is a bigger girl and I have a small member and I am unable to reach inside her any other way. But in this position also, it's still difficult (we only do it on the bed, neither of us standing up). In this position, I have to kneel and prop her up against my legs so I can get inside of her adequately. But it puts a lot of tension on my lower body and its very uncomfortable and I am physically unable to climax because of it. And what we've been doing is, after she's done, we'll cuddle and she'll pleasure me a-nally while I masturbate to finish myself off. Also I notice when I am standing up and masturbating, I find it extremely hard to climax too. So idk whether it's the physical tension on my legs that makes it detrimental to my pleasure or what, (because I have no problem sitting down or laying on my back and climaxing) but I'd like to figure it out so we can completely enjoy each other.
Another thing is I can't really feel her that well when I'm inside her (she can definitely feel me though

) unless she's clenching down with her muscles extremely hard. Idk if it's cause I wear a condom all the time and that's taking the feeling away or if I really am that small. Either way, it's another reason I can't cum.
So I was wondering if these quirks are normal? And if yes or no, is there a work around? And also, this is the first and only girl I've been with before so idk if happens with or to anybody else.