Have 6 thyroid cysts some that are 5cm a few are 2 mm. ..should i have my thyroid removed?

Depends: If benign cysts and the are not bothering you or giving you any symptoms. Ask your doctor.

What you have: Is called a multinodular Goiter. if there are no predominant nodules, observation and follow-up with ultrasound twice a year is ok... If there is a predominant nodule or any symptoms such as hoarseness, difficulty swallowing or esthetics, it could and should be removed. A biopsy of a suspicious nodule would also be in order

Cm or mm: It depends on if they are causing swallowing or compressive symptoms already. A pure cyst is not cancerous so it's now depends on if they are causing symptoms. mm cysts should not cause any problems whereas a 5 cm cyst is quite large and could be problematic.