My mother has told me my sister has mono (tho I doubt it but still) and I think my sister used my toothbrush without me knowing (its on the floor, not in the holder) even tho I asked her not to. Could I catch Mono from her using my toothbrush? (I haven't used it today out of that fear)
Yes you can because it can be transferred by saliva. I would suggest just throwing away the tooth brush and buying a new one because even if she did use it without having mono thats still bacteria from her and its not hygenic. Also if it was on the floor thats a reason in itself to get a new one. If you get a new toothbrush and can't trust your sister with it then you will have to hide it, buy a toothbrush case and you can store it in your room somewhere safe.
I dunno, I catched stereo one time.
yes.