help much appreciated

there is a guy at my school, two grades above. we used to msg all the time, talk at school and i started to really really like him. i thought it was going somewhere, and then he just stopped talking to me. We have a single class and together and we occasionally make small talk. i dont want that, i want back what we had and i dont know what i did wrong. i still have feelings for him, i always find my thoughts drifting to him or find myself staring when he is near by..sigh someone help please. what should i do?