HELP PLEASE

I had sex after my fertile window at the start of December.

My period was due on the 15th however it didn’t come so 5 days late I tested and it was negative.

The day after testing I had slight bleeding so I waited to test again

I tested again and it was negative.

After, I had slight brown discharge, hardly any blood.

I have taken a further 2 tests,

One was taken 4 weeks after sex and the other 4.5.

My period was due yesterday and it hasn’t came yet however I have cramps.

Any advice?