supportworker white van idiots hurling abuse are just jealous because they are stuck in their dead end jobs and on their way to pick up their big macs. Forget em.
Apologies for repeating myself...I used to find running incredibly difficult and it resulted in horrible stiffness, totally out of proportion to the distance I had covered or the speed I managed. I lost a lot of weight and it helped a little, but not that much. Even walking would be hard sometimes. Eventually found I was hypothyroid and that also caused me to be anaemic (which affects muscles and oxygen) and that I need extra iron for exercise. No idea if that is relevant to you, but hypothyroidism is very common, and usually relatively easy to treat, as is anaemia.
If it is just that you have been out every day for the last 7 days and done fast 3k- 5k runs without any walking, it is probably minor muscle damage and you just need to rest and let the muscles recover and then pace yourself and give your muscles more time off between runs to build up strength.
If you get a virus, many doctors advise to give it a couple of weeks at least after you are better, before you run.