As for what you can do right now, please talk to your student services department as soon as possible. They may have a staff psychologist or psychiatrist who can do the necessary diagnostic testing on you. If you’re diagnosed with ADD, there will be supports available to you (e.g., someone to take notes in class, so you can focus on absorbing the content of the lecture).
Even before you’re tested, you should talk to your professors about your difficulties. They may give you an extension of the deadlines, and extra help, so you can get a better grasp on the material.
Some of us learn differently from others. When you have ADD, you often find it much easier to learn when the material is discussed in class, than in a standard lecture in which the prof talks and everyone takes notes. If your classes are lecture style, then meet with your prof and/or T.A., to discuss the material together.
As for how to make yourself study, try setting a timer for 15 minutes. During that time, you turn off all distractions, and just study. 15 minutes is a really short time. Tell yourself that you just have to concentrate for 15 minutes.
When the timer rings, set it for 5 minutes, and do something physical, even just jogging on the spot. When the 5 minutes are up, do another 15 minutes of study, followed by another 5 minutes of movement. Repeat several times.
Those 5 minutes of movement are important because they freshen up your brain and make it easier to concentrate.
I only wish I’d known this stuff when I was an undergrad!
Good luck! And remember, you’re among friends here!REPORT ABUSE