7dpo painful sex (possibly tmi)

Anyone experienced this before?! 
I've been feeling super tired and had a weird pain between be armpit and breast all day. Just feels really sensitive. 
Anyway, this evening the pain during sex was so bad we had to stop. Barely got going at all! My husband said it felt different - like super tight and closed up. 
Any ideas what this could be? A sign that AF is nearby maybe? 
Thanks!