Why is it taking my federal taxes so long to come? I got my state a month ago!

Check here. 

https://sa.www4.irs.gov/irfof/lang/en/irfofgetstatus.jsp

Only the IRS can answer that.   You can start checking on the status of your refund within 24 hours after they (the IRS) have received your e-filed return or 4 weeks after you mail a paper return.   

• Where’s My Refund  will give you a personalized date after we process your return and approve your refund.   The tracker displays progress through three stages:

1. Return Received
2. Refund Approved
3. Refund Sent

To use Where’s My Refund, you need to provide your Social Security number, filing status and the exact whole dollar amount of your refund.   About "Where's My Refund?"

What information is not available?

Amended Tax Returns - Refund information for Form 1040X, Amended U.S. Individual Income Tax Return is not available on Where’s My Refund. Use Where’s My Amended Return? to get the status of your amended return.

IRS phone and walk-in representatives can only research the status of your amended return 16 weeks or more after you’ve mailed it.