Motivation to lose these last 20 or so pounds?

I've already lost a little over 40 pounds over the past 2 years. But I definitely have some unwanted body fat left and some muscle to gain. My boyfriend is leaving for Basic Training in a week, he'll be gone for 6 months so 6 months is the time frame I am giving myself. When I lost those 40 pounds, I wasn't really doing any exercise. But I know that to lose this last 20 or so, I need to exercise and to work harder at eating healthy. But I've entirely lost my motivation. I get these spurts of about a week where I workout and then get lazy and quit for like a month or longer. I know that if I had the "Insanity" program (which I love) I would be constantly working out. But I don't have the money for that kind of thing. I just need to make up some sort of program and stick to it. But my motivation to stick to it is what is holding me back. I think that being with my boyfriend, and his support would be so much more helpful but I want to be able to accomplish this myself. He is very good at taking care of his body internally and I don't want that kind of pressure, to be honest. So when he visits on Christmas break, it'll be a surprise to him. Anyway, I'm looking for my motivation back. All ideas are welcome, please I really need to feel healthy and confident, I'm tired of waiting around because I can't find motivation strong enough. Anyway, thanks in advance for all suggestions. :)