My ex is asking for my tax returns to increase child support. It has been 3 years. Do I need to send her these or get an attorney?

The answer is "maybe" and the first thing to review would be your existing court order.  If it calls for production of tax returns, etc., then that is the controlling order.  If not, she has no per se right to your financial documents, and the court rules state that a party has to ask to open post-trial discovery.  That said, cooperation might be less expensive than litigation.  Another complication is that the applicale child support statutes change in just a few days (February 1, 2020).  We will be updating the information posted on our child support page, here, quite soon, to reflect those changes. It seems very likely that your best course of action would be to consult with a family law specialist well versed in this subject, and decide how to proceed based on a full anlysis of your existing orders, and current facts and circumstances.