I hate feeling this way

In high school i didnt have a lot friends. Most of the time i just sat there in class did my work and didn't socialize with anyone. Now that im 21 i want things to change. I have friends but sometimes they like to go off and do their own things and i feel left out most of the time. When im not with them i just stay at home all day, bored and play xbox alone. The only time where i didnt feel this way is when i was dating somebody. Who knew only one person can make a huge difference in life. But now theyre gone, and i have no one. I only have me, and itll always be only me.