Last Sunday I received Communion even though I knew I had commited the sin of sloth, because I didn’t really feel I’d helped people or studied religious things, like the Bible. I wasn’t sure if it was a grave sin, but I received Communion anyway. After that I felt guilty, so my question is, if you’re not sure if a sin is grave should you receive Communion?
A general rule of thumb is that you should not receive Communion if you *know *you have committed a mortal sin. Mortal sin requires grave matter, full knowledge, and full and free consent of the will. From your description, my guess would be that your actions (or lack of actions) were not grave. In that case, a sin, if there was a sin here, would be venial and you could receive Communion.