When is a good time to take a test and Should I worry Im pregnant?

Ok. So mean and my boyfriend had sex. Once one friday the 19th and then on sat the 20th. Now, I did some reasearch and it says not to have sex on the 10th or 18th day. I had sex on the 8th and 9th day after my period. We did use a condom. Both times. In fact. I thought he put the condom on wrong so I made him switch to a new one. Now, there was only precum and I don’t believe that there was any on his fingers. I watched him closely. He did all the steps to properly put on a condom. My next period is due the 7th or this month. I usually get it early. Last time we had sex, I got it four days early and it lasted the rest of that week. I dont know why I am so scared this time, or every time. This WIll be my LAST time having sex for a long time. Please don’t send rude comments. That doesnt help me. I took a test today, which is the second. It would’ve been two weeks from the last time we had ex one that friday. It came out negative. When should I actually use a test? Also, do I have any reason to worry? After each time we had sex, I made him look at the condom to MAKE SURE nothing leaked or went through, and he said nothing had. I was also in the room while he did it to make sure he wasnt bsing me. SO please, and thing to relax my stress or to atleast bring down my fear a little bit would be so nice.