Nervous wreck :c

So my pregnancy has been considered high risk since day one. I have weekly or bi-weekly visits with my doctor to hear my son's heartbeat and make sure he's doing fine. He's measuring along perfectly and moves so much I thought everything was fine with us. Yesterday, I went in for my visit and got some really heart breaking news. I'm 26 weeks and have only gained 2 pounds this entire pregnancy so far. My doctor seemed really concerned and has asked me to go in Monday to visit pre-term labor with him. This literally broke my heart in two. I walked out almost immediately after hearing this and forgot to schedule my appointment. They called me about an hour later to let me know my appointment time on Monday and explained to me that my baby is fine and this is for my own safety and health. They explained to me that I've been monitored so closely for me, not for him. I'm only 20 years old and there is a risk of me either dying or my body going into shock since he's been taking all of my nutrients that enters my body and breaking up my stored fat because it's not enough for him. Although I'm still processing this, I feel sooo guilty that he's going to have to be in nicu since they're estimating around 34 weeks the most that he can stay in without any long term effects or problems for me. I don't think its fair to him and I've been beating myself up about it. I mentioned it to my friends and they didn't really seem to care. I'm sure they do but I didn't feel better or get the answers I was looking for from them. I was wondering if anyone else is going through this or has gone through this? This is my first child and sadly, will be my last since my doctor informed me it isn't safe for me to get pregnant again. I just need some words of encouragement, because my son isn't even here yet and I already feel like a bad mother. I'm sorry this is so long, kinda spilled my heart and hurt out on this one.