You are probably more attractive than you think. In my experience online dating is a bit lopsided: The only thing you have to go by is looks and a few sentences in a profile. Men are visual creatures so we are easily swayed by a beautiful face. Also, there's the expectation for the man to take the initiative. The result of this is that women feel they are being chased by dozens, even hundreds of guys when using online dating apps. The women are drowning in messages and so they become extremely picky, way pickier than in real life. The men, in turn, notice they are not getting many matches and thus lower their standards to include women they wouldn't date in real life - which in turn makes women even more picky. It's not a good situation for anyone: The guys hardly get any matches (unless they are in the top 5-10% of looks) and the women get flooded by often creepy messages.
You said you are also approaching women in real life. Have you tried social circle, i.e. getting to know the (female) friend of a friend? Social circle is the most natural way to approach a woman in my personal experience. Cold approaching might work but there's been so many guys who are into pickup lately that women tend to get more and more annoyed - every other guy is a "pick up artist" these days and women know the tricks by now.
From personal experience: I work out regularly like you and I usually get warm reactions from attractive women I meet in real life (I've been very chubby when I was younger and didn't have good looks at all). I'm definitely not a model, just an average guy who's putting some energy into staying fit. But online dating has been horrible for me. The only women who showed actual interest online were very unattractive and of way lower quality (in terms of personality, too) than the women who show interest in real life. Maybe that's just my personal experience but I wouldn't recommend online dating at this point. Or, at the very least, don't expect it to be a reflection of your attractiveness in real life.
I also wanted to take this opportunity to send you my best wishes. I hope you'll be well and healthy again, soon. Stay strong, Curl! We're all with you and cheering for you on the sidelines.
