DRY Vagina

Okay guys so I'm 16 weeks and me and my man had sex last night but for whatever reason my vagina was sooo dry and wouldn't stay wet... I wasn't really horny before we had sex but even if I'm not once we get started my body will follow but last night it wouldn't. It was so bad that my vagina actually swell up from the friction so we had to go anal so that he could....💦 so, I'm wondering why did this happen or if it has anything to do with me being pregnant??? 
(I'm gonna post this question in a few chat rooms so I can get a variety of answers, I'm so lost)