Welcome to the board. You're on a good start by losing 18 pounds--but as you probably know by now--heavier people lose weight fast at the beginning and then it starts to slow down the closer you get to your goal weight.
Then sometimes we hit weight plateaus--doing everything right but the scale won't move.
For me--while goals are good--I really don't set time limits on those goals. Some get frustrated and just give up if they don't meet every once of that goal, and others are so elated if they reach the goal on schedule, that they reward themselves with food--a lot of food--which often times explodes their weight to even higher than when they started.
Remember weight lost slowly tends to stay off while rapid weight loss can be gained back twice as fast as a person lost it. One to two pounds a week is the real success story.
Stay with your plan, it's working--but be very careful. This is a lifetime commitment attitude change--and you don't need deadlines. So if your 50th birthday party comes along and you still have weight to lose--so be it. Just keep going, and stick with what's working and you'll get there--and stay there--because of your lifetime commitment to a happier--healthier you.