To cut a long story short, I was given naproxen to see if the anti-inflammatory would help on my chest.
However, the cramping started all over again. And I'm now back in bed unless I need to get food/toilet or wash occasionally.
I googled if naproxen have any side effects and I saw that chest pains were a huge no no.
So I've stopped taking them and I'm going to take it up with the GP tomorrow (who have been avoiding me for weeks which is exhausting).
I'm glad I figured this out. I feel a tad better now already. But BOY that was scary, I thought something was going wrong.