How long before my podcast is added to iTunes

There's no hard and fast answer - it just depends on how busy they are - but quite likely two or more weeks.

I submitted my podcast on February 24,2014. Itunes got back to me in a couple of days, with a confirmation it was under review. Here it is mid-April, and I haven't heard back from them. Any suggestions as to what I should do?

http://paralleluniverse.podbean.com/2014/03/10/parallel-universe-news-round-up-3 1014-s1-ep30/

Presumably this is your podcast?

https://itunes.apple.com/podcast/parallel-universe/id828242020