I inserted an iud in december 2020. now am always urinating all the time but no pain anywhere or fever. is it related to iud or it's just a uti. what can i do to prevent it from happening again?

IUD six months ago has nothing to do the current UTI, if present. I do not understand what you meant by "urinating all the time". Lower UTI or cystitis (bladder infection) causes frequency (the urge to pee quite often), pain or burning with voiding and likely cloudy or blood tinted urine, sometime with foul odor. Some diseases such as diabetes (DM, DI) can call polyuria (urinating all the time).

It may be a UTI, however you should first make sure that you can palpate the IUD string present in the vagina. Secondly, you need to see the MD who placed the IUD to make sure that it is properly located inside the intra-uterine space and has not migrated outside that location and into the bladder which will cause a recurrent UTI.