Feeling Mentally Ill

This is the first time I've posted anything like this, but I don't know where else to turn. I've experienced anxiety since I can remember, but it's just been recently that I've been experiencing episodes where I just feel nothing. This year has been incredibly mentally taxing on me. My peaks and valleys have just been growing closer and closer together and my peaks are short-lived, while my valleys feel like they last forever (although they only last about a week or so). I feel like in the past years, I've lost a lot. My dogs passed away within a year of each other and I've lost so many friends that I thought would be there forever. So I feel like no one sticks around in my life and I just want to abandon everyone, including the most important people in my life. I feel like that sounds so superficial, but for me, it's been incredibly tough. I woke up this morning and I just feel like there's a part of me that's dead. This is one of the first times in my life where I actually feel mentally ill and I don't know where to turn. I know I need to be patient with myself... and know that I'll get better. But it's so incredibly hard to feel like I will. And I guess I just need some encouraging words. Thank you.