worried and would like an opinion!!

hi ladies, so I am on Paragard currently and I am having a really strange experience, my SO and I had sex multiple times Jan 2-4 with him finishing inside, so on the 9th I went to my gyno to get checked out to make sure my strings were okay, they said everything was perfect, my last period was December 10th, and it's the 13th and I have tender breasts and bloating like crazy so I took a pregnancy test just to be safe, and it came back negative, can anyone tell me what's going on?