well maybe somebody could help but.. i've working out for about 4 years of and on.. and i got stretch marks but it was minor... it blended in with my skin color now.. recently i've worked out every now and then cause of school.. and i have some other stretch marks but they are light red... Why is this? Its all around my armpit area...I mean i do stretch before work out.. What you think could be wrong?

also on the innerside of my bicep near where my arm pit and bicep meet there ar red marks along with stretch marks i had in the past, but those are blended in with my skin color.

any thoughts? let me know.