I know how crazy this sounds and reading what I've written reinforces that. But still, those thoughts linger. I haven't sought help.... where would I go? The doctors? You can barely get through the door to see a doctor at the minute.
The key phrase there is "those thoughts linger". You've actually hit the nail on the head there that what you've got here is not a contamination problem (to be solved by cleaning etc.) but a thoughts problem - intrusive thoughts.
The trouble is your mind reacts to the intrusive thoughts and anxious feeling and interprets it as a sign of danger, so making you feel even more anxious, so you get a vicious circle. The problem isn't the basic aim of wanting to deal with contamination risks - the problem is that you have anxiety that persists and grows even after you've taken the basic steps you need to do to remove the infection risk.
Then your mind goes over and over, round and round, trying to think its way out of the anxiety, or you take more and more cleaning steps to reduce the risk from the situation even more and get rid of the anxiety even more.
The trouble with this level of anxiety is that it's just not possible to do enough, or think enough, to get rid of it, that way. You need to try to ignore the anxiety - step back mentally, notice that you're feeling anxious, try to just observe that dispassionately and then let the feeling flow through you and out the other side, without you taking any special action.
It is really really hard, your mind wants to resolve it, remove the feeling completely somehow, but when you've got this much, it doesn't work.
Try saying to yourself sometimes "I've got really strong anxious feelings right now, but those feelings won't last" - and let the feelings exist for a bit without trying any other action (like cleaning, or thinking round and round in circles about it). It's not a quick solution, there isn't one really, but if you can manage to do it, it will definitely help.
You should be able to get a GP phone appointment. Some antidepressants can really help with this sort of anxiety. Read about OCD and intrusive thoughts, too. Good luck.