There's nothing to feel guilty about - sick leave is just that, for people who are sick. It's not like you have no intention to return and you're just waiting to get yourself balanced again. What good are you to the team if you're not able to contribute? As harsh as it sounds (i don't intend for it to sound that way), the team will survive without you as will the company so use this time to get yourself back into a place where you can function effectively and enjoy life again. Mental illness is very real and can have devastating consequences if not dealt with effectively, it sounds like you have everything in place you're just waiting for it to work. Be patient and be kind to yourself. You need to let yourself recover. Eat healthily, establish a day time routine and sleep a set number of hours. All the best.