Overthinking. Because he is getting sex?

Dr, i am a medical student myself. And i have a prob of overthinking. A guy, lets call him S. S and i have been best friends for 10 years. We were in a relationship for an year in those 10 yrs which was the most perfect time. We would talk everyday before but some probs started between us later, n we broke off. We were still the best of friends. But we would talk only once or twice a month. Last march, we began flirting and sexting, opening up more about our feelings, which brought us closer. I cherished all of it. I knew it was love. But still a voice inside me sometimes said "why are we talking more now? Is it because of sex? Is it because he is getting sex?" I knew he is not like that at all. I knew he loves me unconditionally, understands me perfectly, does so much for me.i tried 2 cnvince myslf.bt dat thot kpt coming. I told hm abt it. Hez heartbroken. Said how cud i of all da ppl thnk ths of all da things. N he said it mks hm thnk wht nxt thot ill hv.Pls hlp me fite dese voices