Please help!

I am 15 and am having an endoscopy and colonoscopy tomorrow under general anaesthetic. Unfortunately my period was late and I started yesterday so it is going to be really heavy on the day of the operation. I haven’t tried a tampon ever but I don’t mind trying if I have to - I don’t know if they let you wear a tampon durning this type of procedure. I normally wear a pad but I don’t know whether I will be able to wear my pants for it. What do you think I should do? By the way cancelling the operation isn’t an option and I don’t talk to my mum about things like this so I don’t know how to bring up the conversation. Thanks in advance.