all the symptoms no positive

So I have had all the symptoms of pregnancy and I am three days late. I normally have irregular periods but last month it was regular. I have been trying to have a baby. could I still be pregant I have sore breasts, nausea, indigestion, gas, and am peeing frequently. This past Sunday I got a positive test but I was unsure about it so I tested the next day and got a negative, and another negative today. I'm not sure what is going on can I possibly still be pregant. Is the hormone level just not strong enough.