Where is this relationship going? Worried sick and afraid to be hurt and loose him..!! HELP?

im 21 and hes 25. He liked me from afar for a year before having the courage to speak to me, He ALWAYS says that he loves me but I tend to question this, not sure why. On our second date, he asked me to marry him as a joke and i jokingly responded.After that he kept on texting and calling me. Two weeks later we had s** and even then he kept on saying he loved me many times. However, after we had s**, he later texted me 'Hi baby I had a really nice time with u and i love u so mach.' - where is this relationship going? Im really confused. Am I being used? Does he genuinely love me? Will this lead to marriage (as I would love to marry him but im sooo confused)? Should I leave him? If so, for what purposes? I am really really AFRAID of being hurt. Ive had bad relationships in the past and dont want this guy to become my 'ex'. Im just so scared where this is leading....PLEASE HELP