Pregnancy scare or something else?

Hi girls! So I just wanted to tell you my story bc im not really sure about what’s going on with my body. So, i have been always regular on my periods the maximum days of delay were 3 to 5 days. This month I haven’t had my period with today according to the eve app I am 15 days late. However, I got really scared a week ago and took 5 different home pregnancy tests and 1 blood test all of them were negative.

The last time I had sex was the 17th of July, which was a long time ago and I think if I could be pregnant , that could be seen on my blood test.

Moreover, I suffer from gastritis and Idk if that can be a factor that could affect my cycle, as bc of this sometimes i am nauseous but i have never vomited, i am also taking pills to control my gastritis.

I am not sure what is happening with my body, I am not taking any other medication or the pill.

What do you think ? Do you think i can be pregnant even-though I had a negative blood test days ago?

Pls help me! Thank youu!!