What are symptoms of an anxiety attack?

I have stopped smoking marijuana (mostly because I ran out, but I don't intend on buying more); however, I have recently relapsed with Oxycodone (50mg). I haven't used anything in a few days and I keep getting these weird attacks. My heart will start pounding and my feet will grow numb, then that numbness will spread throughout my body and I'll just get nervous. Am I having an anxiety attack? It'll last anywhere from a few minutes to a few hours and they come and go a few times a day. If I am suffering from anxiety, how do I cure this?