Help anyone? Very stressed 😔

Hey ladies so I had unprotected sex about 16 days ago and he pulled out I didn't take plan B and 10 days afterwards I took a test and it came out negative then on the 16th day(today) I took another test and it was also negative. Although I think I had some spotting or its just my period because I'm very iregular. Also I had lower back pain once or twice. Could I still be pregnant? Both test were negative.
Please help?!Â