HELP PLEASE IDK

My periods are always regular always every month come on the day it is expected to. Yesterday morning I was bleeding on the tissue when I went to the bathroom. It wasn't really light but it also wasn't as heavy as my normal period. Checked right after and nothing. I would say about 6-7 hours later there was blood again. Checked for the rest of the night and nothing and still nothing this morning. This has never happened to me before and that's the only reason why I'm wondering could I possibly be pregnant ? I had sex on the 17th I took a test it was negative. SOMEONE help me what should I doooooo