Crown keeps coming off. Tired of going to the dentist so often, having x-rays, molds, .. etc! What are my options?

I had a root canal done to the back molar on bottom right side and what's left of it is very small. The doctor indicated a crown for that tooth which he did. While I had the temporary crown it wouldn't stay on for more than a day. After the permanent crown was 'permanently' cemented, the crown came off apparently together with what they call buildup. Since the the crown doesn't seem to stay in place, what are my options? Do I even need that tooth? Would simply removing it be a reasonable solution? Thanks.