idk wtf is going on

Sarah • Wife. Momma of 2 boys. (Nov. 2014) (Sept. 2016).
Valentine's Day my husband and I were both super drunk, swears he pulled out but I think he was a little late pulling out.... My period came on the 21st of February (it was a week early) and it was very light and lasted 3 days. I thought it was odd but didn't put much thought into it. I'm now 9 days late, all pregnancy tests are negative, but I've only been using those dollar HCG strips. 
Any advice is welcome... should I get a blood test? I've never had this happen, home pregnancy tests have always worked for me