I'm sorry your having such a hard time concentrating. I always have to deal with this when I get depressed. I don't know any full proof ways for getting through lectures, but I do second the doing two things at once, such as reading and watching t.v. That's how I do it. Also one thing I do is I try not to stress out about loosing my concentration. When I realize that I have I just direct myself back to what I was working on before. I know it will take longer but this way I don't get angry with myself for getting distracted. The other thing I do is I cut things that I have to do down into really small steps. If I am reading a text book, it may be reading three pages, instead of a whole chapter. If it is writing a paper, I may make my goal writing two paragraphs. Once I have accomplished those I take a very short break and then come back and concentrate on what I was working on. Or if I have a real lot to concentrate on, I will work on one thing (writing a page) then reading then writing again. This way I am taking breaks from each individual activity, but still continuing to get work done.

Good Luck!