I seem to get it every summer. It's miserable.
Use Zanfel if it hasn't been too long since you were exposed.
Works amazing but is pricey (like $40!!!) and only works to remove the oil (urushiol). It is a cream/wash, works better than anything (seriously) and you should be able to get it at cvs or so.
You will probably have to get a subscription for prednizone like mentioned. Benedril has never been that effective for me.
You will also probably think it is spreading, its not really, your body just reacts differently to different exposure levels so you break out where you were exposed to the most initially, after that stops itching (scabs over whatever) you will probably be breaking out in new areas. Miserable like I said.
The last time I got poison ivy from weedwacking I didn't sleep for a week. Cold can help the swelling go down, so ice and cold showers will help the reaction a little.
Good luck