Should I worry about pregnancy if I had my period on June 25 after intercourse on June 6, and now (12.07) brown spotting and dark clots have appeared?

In the presented scenario, pregnancy is unlikely. Postcoital menstruation and subsequent ovulation indicate a new menstrual cycle. Brown spotting and small clots on July 12 can be associated with hormonal disorders, changes in the endometrium, or minor irritations.

There is no need to worry here, but if the symptoms persist or worsen, it is worth consulting a gynaecologist to be sure. If you are not able to make a face-to-face visit, I attach a link to the online teleconsultation:

https://www.gdziepolek.pl/telekonsultacja/z-ginekologiem