Sorry chills, I know how frustrated can be when nobody answer...
Well, what I could search (I am working you know...) , yes your priority date is the one that is on the I-797C Notice of Action. By USCIS glossary:
Priority Date - In the USCIS Immigrant visa petition application process, the priority date is the date the petition was filed. If the alien relative has a priority date on or before the date listed in the visa bulletin, then he or she is currently eligible for a visa.
If you have your notice of action (receipt) from your I-130 in the upper right corner should be your priority date and should be near the time you filed or the receipt was made.
Hope it helps!