How do I tell if a guy really just isn't into me? New at dating and I don't know what to do, advice please

Seems like common sense, I know. I went to college with him and we recently reconnected, and we started hanging out and after a couple months we slept together. It seems like a fwb to me I guess. He's 29 has 2 kids by 2 different women and I'm 24, was a virgin. After the 2nd time we had sex it just seemed like he was pulling away, he used to kiss me and there was tons of foreplay. After the first few times I initiated the sex and there has only been foreplay benefiting him. He said recently he feels out whatever it is is just sex and our friendship is disappearing. I told him I felt the same way but that I wanted more than sex. I want a relationship eventually but he said it's just going too fast already for him and he barely texts me anymore. Anyone care to give advice? I honestly don't have experience dating and I'm not sure if all he wants is friendship. Please help a girl out, I don't know what to do