Does pregnancy cause horrible sex???

I usually always get really turned on and always orgasm when my so and I have sex but since we started having sex (waited til 12 weeks, I'm 20 weeks now) I haven't been able to stay turned on or orgasm. Its really upsetting cause we have really great sex and now, since becoming pregnant, my body just can't even stayed turned on?? There's nothing wrong with the sex, we've even tried countless positions but nothing works for me. I feel horrible I just want to enjoy sex lol and I'm usually horny until we start. Is anyone else having this problem or am I crazy?