so i'm 17 and started working out with fitness blender about a year ago and i've gained so much in strength, flexibility and endurance but a couple months ago i started working out with dumbbells and recently i have started to have so much pain in my lower back and some times it's fine when i'm doing cardio but when i do a strength workout it hurts again and i've checked my form and i don't see any issue with it. my knees have also felt weaker somehow. i feel like they've gone weaker since i started strength training. i hear so many pop sounds when i bend them.

i don't know what i should do. should i stop strength training?