Smile, it's all under control...
A good place to start is to make a big list of EVERYTHING you need to do; any deadlines you have, events coming up, or even just something you want to grab from the shops. Then divide your list up prioritising the most important. Putting everything in an order and knowing what you have to get done first will stop you stressing too much about the less important tasks.
Then, from your list, give yourself a target for the week making a note of which tasks you want to get done each day. Tick them off as you go so you feel like you are achieving something. Well done you.
Use a diary, they’re great. I’m a little biased because I haven’t figured out how to use the calendar app yet, but I think having a hard copy of everything you’re doing is very useful. However you choose to store the information (digital or otherwise), keep track of everything so you can easily spot any deadlines you may have creeping up.
Set time aside to organise your notes, it may not seem so important when you have a lot of work to get done but knowing where everything is will make you feel so much more on top of everything and it will make things easier when it comes to revising.
Last but not least... even when you have a very busy week with lots of deadlines make sure you set aside time for yourself - do some exercise, meet friends, don’t just drown yourself in work. You’ll be less productive if you don’t give yourself a break and it will be really really boring.