i forgot to send my husband an original Birth certificate n i only sent him a copy of the original..... wd they accept it??

Who knows, but probably not. If you sent a photocopy only you will probably get an RFE for the original.

how long does it take them to send RFE?
do i have to wait for it?
or shall i just send the original?

As posted in the other thread that you created... If it is not a certified copy, then you will probably receive a RFE for the original. You can call the NVC hotline to find out when the RFE is available (if indeed you get one) and at that time you can send the original (if requested). Be sure to include the DS-230 coversheet from online (provided you paid online). If not, you can use James's shortcuts to create the coversheet. If none of those help, just wait for the RFE paperwork from the NVC.

if we are the sponser do we need to send our birth certificate somewhere????

And, I'd suggest waiting for the RFE before you send your original copy.

No, not for the DS-230. You just need to send your beneficiary's original birth certificate.