IRS requested additional papers which I sent certified mail and I wonder if they are processing my refund yet ?

You will have to monitor your federal tax refund status on the IRS website - https://www.irs.gov/refunds

As @DoninGA stated, you can check the status of a refund at this IRS webpage.      

See also this IRS webpage for more FAQs and more information. The fact that you submitted additional information by mail at their request will add to the processing time.

Some tax returns take longer to process than others for many reasons, including when a return:

• Is sent by mail
• Contains errors or is incomplete
• Needs further review in general
• Is affected by identity theft or fraud
• Was referred to the IRS by the bank due to suspicious activity
• Includes a claim filed for an Earned Income Tax Credit or an Additional Child Tax Credit. See Q&A below.
• Includes a Form 8379, Injured Spouse AllocationPDF, which could take up to 14 weeks to process

For the latest information on IRS processing timeframes, see their Processing Status Dashboard.

@j4w