gonna need some info, such as potting mix, last time it was repotted, fertilizer schedule, how much light, indoors/outdoors, etc.

Potting mix was probably something from a "potting soil" bag, last repotted probably 5 years ago. Fertilizer has been standard miracle grow all the houseplants get. Lives in a North/West corner window and typically has done better there than when I've put it outside for the summer. So now it stays in all year. I don't want to go up in pot size, it's big and heavy enough.

after all the blooms are gone, you could try repotting. it's most likely very root bound, do a little root pruning. and maybe prune the top too. i'm thinking a large bonsai, do a search in the bonsai forum for citrus.

the tree itself may be doing ok at a NW location. I would suggest a S or SW location for more light for fruit. most citrus will bloom profusely, set a bunch of tiny fruit, then drop a bunch that it can not support.