I thought I’d add my experience, as (touch wood) I seem to have been lucky so it might give some other people hope that it isn’t always too bad. For me the whole thing has lasted a week.
Day 0 - horrendous headache, didn’t realise at this point that it was covid. I was also tired, having an afternoon nap, which is unusual for me.
Day 1 - horrendous headache continued, joined by a sore throat. Still tired.
Day 2 - Headache was less, sore throat continued. Completely exhausted, I barely moved off the sofa. Tested positive, but have numbered the days based on symptoms, not on when it occurred to me to test (and I pretty much only did the test as I was due to see people that have vulnerable family members).
Day 3 - Exhausted, shaky, sore throat, unable to regulate temperature (either freezing or boiling, no in between), so incredibly snotty and bunged up. This day felt like a really bad cold.
Day 4 - same as day 3, but feeling slightly better as the day went on and less exhausted. This day felt like a pretty standard cold.
Day 5 - much better, only slightly snotty (and not bunged up at all as the day progressed), no sore throat, appetitive returned, more energy. This now felt like the tail end of a standard cold.
Day 6 (today) - woke up feeling back to normal. I did a test today and it was negative.
So although there were a couple of bad days, it was thankfully quite short lived. This is the second time I’ve had covid, and I’ve had the vaccines and boosters, so hopefully all of that prior immunity helped. I did lose my sense of smell, but it already feels like it might be coming back.