Health Anxiety

I have recently had a horrible illness which went on for a month. It started with a migraine and severe fatigue then led to stomach cramps which came on in waves then I was hit with severe diarrhea which after a few days turned grossly bloody. The diarrhea returned to 'normal' colour but I dealt with it for 19 days and was even gping a to the bathroom a few times in the middle of the night. Stool and blood samples all came back clear at the doctors although they were done late on on the illness so maybe too late to detect anything. When I first started to slowly recover, I was grateful for everything. Even going to work, being able to eat, being able to sleep through the night....now, I just feel horrendously down and unsettled that I never knew what caused it. I am also terrified it will happen again and am paranoid about food being undercooked to the point of it becoming quite distressing for me. Am I being unreasonable or stupid? I thought I would be over the moon that I am okay now but I don't feel positive or happy at all. Just very unsettled and anxious.