So my boyfriend was my first and I was his first (our first was last month), and we've had sex about 5 or 6 times since. But since then he's wanted to experiment with positions, which I'm totally fine with. Although when it came to cowgirl and reverse cowgirl (me on top) my legs get so tired. And I feel bad because I can't last that long on top, but I can tell he really wants more, since he's usually the one doing all the work with Missionary or doggy. I was wondering if I should just exercise my leg muscles more? Or are there other positions that could help where he doesn't have to do all the work?