I wouldn't double my workout. That's a pretty substantial change. Just make changes (if they're even warranted, which they might not be. I like the advice above that if you're eating to plan, you're good. If you're not, then get back to eating to plan) - anyway, if you're going to make changes, esp if they're warranted, then make ones you can live with long term. Yes - I could get back to my lowest weight - 138 lbs. But that would mean substantially cutting my current calorie level and/or really beefing up my fitness routine. Am I willing to do that, possibly permanently? I wrestled with this for a long time and finally decided no, it's too much of a struggle for me. My body seems to want to be where it's currently at. And I'm OK where I am. But it took me awhile to get to that point mentally.
nevertheless, if you're eating according to plan, you may not be done losing. Those last 20 lbs are so are notoriously tough to get off. Remember I said I had months near the end where I was only losing 1-2 lbs a month, despite working pretty hard at it.