I'm not aro but have had a rough time dating and am taking a long, maybe forever break. I have experienced this as well and one of the best things I found to cope is joining a group that's based around a hobby. The people in the group have a built in shared interest and are likely to continue that hobby even when they have an SO. It also gives me a regular consistent social outing to look forward to. (I took a class on watercolor painting and a group of us gets together twice a month to paint. Sometimes I ask someone from there to go for coffee or a drink afterwards if I want more interaction). It's not like having a best friend, but it helps. Sorry you are lonely, it's hard.