It’s taking a toll on our relationship - what could it be

So my boyfriend isn’t really eating he has zero appetite he says his stomach is always turning and he complains that his legs are always aching and hurting ( it made him cry the other night) and I’ve never seen him cry before.,

I had these horrible aches and pains a year ago like they were in my bones and I was in bed for almost a month turns out it was b12 and vitamin D deficiency and I had to get the 3 jabs.

I’ve tried helping him by getting multivitamins and making him rest he’s been this way not eating for a couple of days now but his legs have been bad for a couple of months, it’s not like he’s super active or not active enough so the only thing I can think of is he’s not getting enough vitamins. He slept from Monday night until Tuesday night and then still managed to sleep that night.

I’m going to book him in the doctors and try to get to the bottom of it has anyone else experienced this?

I think the not eating etc is a stomach bug but the only thing I can think of for his body aches are a vitamin deficiency so will ask for them to take blood and check, anything else it could be that I should mention?