I’ve gained 5 pounds over the past 4 days, whilst eating in a strict deficit, often leaving over 500+ calories on the table. What is going on and what can I do to fix this?

For context, I’m at 150 pounds right now, but had gone down to 145 last Tuesday. I did get Covid on Sunday and battled through it this week, and maybe that’s the reason for the sudden weight gain, but either way this is really frustrating. Ive been logging my weight every week, and this app gave me a specific calorie plan to follow where I’m even going light on the daily calories to begin with. What do I even do here? I poop probably about three times a week, but my stools are pretty hard and I often don’t pass a lot of substance. Would anyone recommend fiber pills? I eat plenty of fruits and veggies, so I shouldn’t have a problem with it to begin with.