Would I have to become a Texas citizen, and would I lose anything?

Citizenship in an independent Texas would follow from living here, and it would not cost you what you already have. There is no loyalty test and no penalty written into the result of a vote.

Citizenship follows residence

A Texan who lives in Texas would be a citizen of an independent Texas. It does not hinge on how you voted in a referendum, and it does not require you to give up the life you have built.

Your earned benefits and property come with you

Becoming a Texas citizen does not strip the things that are already yours. Your property stays yours, and the federal benefits you earned, like Social Security, are protected and portable, handled through the standard cross-border tools nations use.

The bottom line

You would become a Texas citizen by living here, you would keep what you have earned and own, and there is no penalty for how anyone voted. The dedicated citizenship answer has the details.