Night flow help!! sorta tmi

Isabella
so my flow for my period is very active, and heavy right now. it's 1:10 AM now, and I'm getting ready to go to sleep. I put on a pad of course but this is what I need your comments on, I always leak through my underwear because, when I sleep I guess it leaks to where the end of my pad is. How can I prevent that because my underwear keeps getting stained, so I'm a the point where I have to buy A LOT MORE?!