Best friend touched me in sleep

So me (13) and my best friend (12) were having any normal sleepover and when he thought I was asleep he took my hand and just put it on his crotch. After 2 minutes he unbuttoned his pants and put my hand on his hard penis (keep in mind he is only 12) and it was huge. Like llitteraly not an exaggeration or anything 11" long and he has barely even hit puberty and had no pubes whatsoever. Now my penis is extremely small 3" hard and I'm pretty developed with tons of pubes and an extremely deep voice so as my hand felt his penis I got hard. While I was stroking his penis he started sucking mine. I came after like 2 minutes and he swallowed. So I kept stroking his penis (both my hands could fit on his penis and there was still like 4" to spare) and I felt his piss (he haven't developed semen yet) drip down my hands. This was the best sexual experience I've ever had and so far it's happened twice more after the first incident. Keep in mind he thinks I'm asleep during all of this. Should I come out and tell him I've been awake or just let the flow keep flowing because I feel like if I tell him it would ruin both our friendship and our sexual experiences