why do men keep trying to force themselves on me

Im an introvert, i talk but im not the type to keep a conversation going for long before it gets awkward. I dont know why but some many dudes have tried to force their way into something sexual with me. im not flirtatious. im just chill and laid back. i feel like men take advantage of my quietness and see it as shyness. I cry a lot but not over men but how i get treated by people. I dont know how to change this. i really just want to live a normal life but its becoming a challenge. i dont know what im doing wrong to where i keep ending up in these situations. i do want a relationship but i dont even know where to start. this sucks. maybe its an age thing? im 19 but the men i talk to range from 20-28.