Can you be pregnant and have negative tests

So I last had sex at the start of February, unprotected.

My stomach hasn’t been feeling great for a while, not sure if it’s stress, change in eating habits and less exercise because of lockdown or what.

My last 3 ‘periods’ were more of spotting than anything else as I normally pretty heavy. I’ve been constipated for a while and feel nauseous a lot. However, I’ve taken 3 tests, the first one 2/3 weeks after I had sex, and was negative. Then another about 9 weeks after and was negative and then one last week, which again was negative.

But I was reading up and found out sometimes you can get negative tests but actually be pregnant. I’m just panicking because I know I don’t feel right in myself and it’s making me so anxious which probably isn’t helping at all! And I don’t know what’s going on