My vision goes black sometimes

So about a year and a half ago, i went to the park with this guy i was sort of dating and we smoked a blunt, i had hit it about two times and then all of a sudden the outside corners of my eyes started going black and it kept getting blacker and blacker, until i finally passed out. he said i was out for about two minutes and i fell straight on my back. i had no idea what it was, but i thought maybe i just passed out because my knees were locked for too long. but then i was smoking with my sister and her boyfriend a few months later and my eyes started going black again, i told them it was happening and her boyfriend told me to sit down so i did, and it went away. a few months after that i was smoking with them and it happened again, this time i was already sitting down. so he gave me something to drink and it went away. it really scares me because it was like i just went blind for a few seconds. a few months after i had met up with that guy again, we weren't together anymore we were friends just wanted to smoke together. we were in his car smoking a blunt and the same thing happened, everything started going black, i didn't say anything to him cause i didn't want to alarm him but i asked to have a sip of his drink but it didn't work so i rolled down the window and it went away thank god. then a few months ago from today, i was at my sisters friends house smoking with the two of them and i had just hit a bong, (the other two times i smoked with my sister and her boyfriend i had hit a dab. so almost everytime it's happened it's been with something different) and it happened again. this time i kinda knew what to do, but it still freaks me out. i sat down, it didn't go away, i drank water, it still didn't go away, so i told my sister it was happening and she told me to lay down so i did and my sight slowly started coming back and when i saw full color again i sat up and i was fine. the last time it happened to me was the other day when my sister gave me a dab, but i immediately sat down and drank a sip of water and it went away. it only ever happens when i smoke THC. i think it's only when i get super high but i'm not sure because the other day i didn't even get super high, just a little stoned (it was a small dab). my sister said that my face gets super pale when it happens too. i read on here that it can make you permanently blind? but i really hope that's not the case because i don't want to stop smoking weed, but i sure as hell don't want to go blind. so what do you guys think this is? should i worry about it or no