Please Advice

from the bottom of my heart I never realized I was going to write one of these and ask her women’s opinions that don’t know my backstory. I am 18 years old and I have been with my boyfriend for 2 1/2 years. The honeymoon stage was great but we have been passed that for a while and it’s not what i have been expecting. we’ve been constantly fighting and i’m sick of it. last year I found him in a car with a woman in a parking lot. He says he wasn’t there to cheat but I don’t trust him since then. He lies constantly to his parents, friends, and I’ve caught him lying to me many many times even though they are small it’s still breaks me inside. When we fight he becomes really aggressive. Not to me but he will break things which scare me. he says he loves me and cares for me but when I’m so scared want to get out of it he tries to manipulate me and say that he’s going to commit suicide and I am the only thing he has. I am in a very toxic relationship I know but I can’t leave I’m scared, and I don’t know what to do if I were to break up with him and he did commit suicide. That burden will be with me forever. Last night we got in a fight and he threw a rock at my car and broke my back windshield. I was so scared it was such a small rock but it damaged so much that my car has to be sold and written off. He said it was an accident he didn’t realize it was gonna break my windshield but why was he throwing rocks in the first place. I just need an opinion on what to do. I’m so scared to leave him as we have done everything together and have talked about the future but i don’t know if this is a sign to break up with him