I feel helpless while my friend is going through a hard time

I wouldn't normally go to the internet with something like this. My therapist is sick and I cant talk to my only close friend right now.

Last Monday I had a particularly bad day, so I started mindlessly ranting at my closest friend, something I normally do to deal with stress, they're good at listening. However, it took them hours to reply to my message, and when they did, they simply said "sorry." I knew something was off, it wasn't them to reply with a single one word message after hours of silence.

Fast forward Tuesday afternoon, I was a little concerned about them but mostly fine. I was busy with work anyways. Then they texted me saying that they hadn't been at work for Monday and Tuesday, and but otherwise "Its nothing, Dw about me". At that point I was worried sick and I almost had a full breakdown.

I late texted them asking if they were really okay and they kept insisting they were. Ofc I didn't believe them, because they were acting very off and it didn't make sense that they didn't want to tell me. We've exchanged very personal secrets in the past.

Its now Wednesday. I restrained myself from talking to them all day, figuring they needed space. I can't find a way to distract myself, and my paranoid brain is trying to come up with every possible worst case scenario. The stress is consuming me, I barely feel anything outside the situation with my friend, I cant be productive with anything, I have really high blood pressure and intense heart rate.

Last night around 1 am I ended my conversation with my friend simply saying "Thank you" after I told them how much I care. I haven't talked to them all day, and if I dont say anything Ill be completely consumed by the stress. I figure I want to say something like "how are you doing" though they've made it obvious that they dont want to tell me about it. If I start with something more innocent like "did you sleep last night" they could take it the same way. One would say to speak from the heart but in that case all I want to say is "I love you" which could get awkward because we're opposite genders but really just friends. I just want advice really. I can deal with the stress, as hard as it may be. What should I tell them? How can I not push them to talk about something they dont want to while still helping them?