AITAH for falling for someone whilst seeing another

I (21m) have since quite some time been seeing a girl (22f, now called C). We had made out at a party once and have regularly met since then for dates/makeout sessions (I didnt really know her previously), although it has to be said, that we are in no way official. I am very inexperienced when it comes to relationship/sexual stuff. Since the beginning she was giving me very mixed signals (asking for meetups but taking days to answer messages for example). I am completely aware that i am rather incompetent at communicating in such instances, which most likely is part of the problem. in the past weeks we couldn't meet due to academic/work issues. I have a friend (21f, now called S) that i have gotten to know for the past few months). Since about 4 days i have been rather sick, which was causing me both academically and professionally some troubles. S has been bringing me medicine and such multiple times, which is admittedly something i am not in any way used to. I feel like im falling for S even though i know i am kind of betraying C. I really have no clue what to do. neither am i sure, whether my feelings are amoral or not. I hope you can help me. Due to my natural bias, give her the benefit of the doubt please