Hello doctor before 5 months i inserted an object into my anus and i was bleeding for 3 days, how can i know that i have not pierced the rectal wall ?

You're brave: All teens / young adults do dumb things; it's part of growing up. If you'd pierced yourself and it hadn't healed, you'd be having some heavy-duty infections in the tissue surrounding it, and it would be obvious by now. You scraped the mucosa off but didn't pierce the muscular wall, which is what usually happens. I'm glad your adventure ended happily and i admire your courage in writing. Cheers.