Could I be pregnant?

Lily • 🐜
Okay so my period is two weeks late, but I've taken two pregnancy tests and they are both negative. I have indigestion, nausea, headaches, fatigue, back pain and I've gained weight. My boyfriend and I have sex like 3 times a week so it could have happened at any time. Side note: I was put on Nexplanon (the implant) about 3 months ago but took anti biotics for a UTI. We used condoms.