Feeling embarrassed and sad

So my boyfriend and I are 18 and we've been having sex for about a year. It's usually awesome. I orgasm every time and we usually orgasm at the same time and both feel amazing. Lately it's felt like we've been doing the same 3 positions: cowgirl, doggy style, and missionary. So today I said, let's try out some new ones. We tried one and my BF was clearly having trouble staying hard, and the sex just kept getting worse and worse. We both agreed to keep going even though neither of us were really enjoying it, and so finally I was like, just cum and let's get it over with. Because I wasn't going to cum. I rode him for 10 minutes and he didn't cum. We both ended up feeling really awkward and embarrassed and it was awful. This is the first time we've had bad sex. I was just wondering, does this ever happen to anyone else? Is it normal sometimes?