So, my last period ended January 8th, and I had unprotected sex the 10th, 16th, and 20th of January. I don't have a regular cycle so I never know when my period is going to come. Then today, the 25th of January I got my period. The day before today was very light, no clotting and a little brown, and I had cramps. So I was worried that it was implantation bleeding.Then the next day (25th) it got heavier and was clotting. I was wondering if there is still any chance that I could be pregnant.

Try taking home pregnancy test if you are worried. It is really risky to have sex after few days your periods stop. These are the high time when one has a high chance of getting pregnant.

Humm, I am sorry for somewhat wrong advice, for most women the fertile time comes about 1/2 way between periods or about that 12th to 14th day.
BUT. Wommen ovulate at different times and days, so the only. And it is the only way to know your fertile days is to be checking it with medical means such as basal temp.

Next it is way to early to do any pregnancy test at this point, also, what is your period doing, it is going to remain heavy for a week ? Or just stop ?

Without knowing a regular cycle, it is harder to determine. But you need to wait about 4 week past the sex date, or 2 weeks after a missed period to do a home pregnancy test.

Always use the first urine of the morning