Needing serious help.

My son will be 4 next month. I’ve been wrestling with how to address this The last I’d say 5 months since he tried to copy my putting a tampon in which he barged in on and interpreted as putting toilet paper in my butt I’ve sent dealing with attention seeking possibly him body exploring?. He has tried that a few times by balling up toilet paper and putting it up against his butt hole, I think took care of that, then dealing with him trying to put a diaper on (he has a little brother and a younger friend still on diapers that I nanny). Then he tried to put diaper rash cream on his own bottom after I put it on his baby brothers then put chest rub on his penis I told him it’s not safe to put things on his body without permission and the chest rub is for the chest and feet only . Brother fell into a toy in the bath a week or so ago and it scraped his butt so I put ointment on it, tonight I caught my older son trying to put a little fish in between his butt cheeks/up against his butt hole. Which is NOT SAFE!!!! He wouldn’t remove it from his crack for himself so i disciplined him telling him that it wasn’t safe and he chose to not listen so that’s why he got in trouble that it’s ok to learn about our bodies but we don’t use things to learn what feels different or not. I remember as a very young child starting to learn certain things felt good on my body, I would hump a pillow, put hot wheels in my undies(lord knows on this one lol maybe the clit stimulation was what this did) and just generally was a very horny child lol. I don’t know if this is him being really curious about his body or seriously attention seeking. I feel like I do an ok job giving him one on one attention as best I can, but I am a nanny and a single mom to him and his one year old brother so it’s busy & they have very different stages of development obviously. I just don’t know what to do. It almost seems attention seeking but he’s learning it feels good in the process? I don’t know I’m at a loss and feeling like a bum parent for not knowing what to do/say.