I know most on here aren't doctors but I'd be curious if anyone here who had taken or before had the same response. I'll probably check with my doc tomorrow but I don't want to come off like a hypochondriac which I kinda am anyway. Still I wanna be safe.
Also another thing I wanted to ask if I have orchitis with it, which by the looks of things I do, could this actually cause atrophy? Doc says continue as normal the heart rate is probably the infection itself.
What are you taking it for? What infection is weakening your heart rate?
Fatigue is definitely a side effect of it - https://www.rxlist.com/consumer_cephalexin_keflex/drugs-condition.htm#what_are_side_effects_associated_with_using_cephalexin
Most things I found by Googling say it increases your heart rate, not weaken it - https://www.mayoclinic.org/drugs-supplements/cephalexin-oral-route/side-effects/drg-20073325
Orchitis can cause testicular atrophy, but is this what you are treating?
https://www.healthline.com/health/testicular-atrophy#causes
If you are treating it, I wouldn't worry about that.