I have cramps, loss of appetite and bloating, am I pregnant?

I missed several birth control pills and also was on antibiotics for a week for bronchitis. My husband and I had unprotected . When I was supposed to start my period I only spotted some, not like my normal periods. No I feel nauseous, loss of appetite, low back pain, constipation, cramps on the left side, and I also felt a small bump on my left side that went away. I took a home pregnancy test that came back negative. I'm not sure if I'm pregnant and its to early to tell or if something else is going on. I haven't started my birth control pills back up yet just in case. Any advice?