I am in a company where I have 5% ownership proven by the tax returns. Can the other 2 owners just take back my 5% withoit my consent?

The rights of the shareholders would be set forth in a shareholders' agreement, which might provide, for example, that the majority owners have the right to buy you out for a set price.  Absent a contractual provision allowing it, the other owners cannot simply confiscate your ownership interest.  Of course, a 5% ownership interest only entitles you (again absent a contrary contract) to a pro rata share of distributions.  It doesn't entitle you to be employed by the company or to have a say in the company's management.