I'm not sure whether my fast for ramadam count. I did not do intention to fast because i was feeling unwell but was able to manage until iftaar

I was having a light fever so I decided to do sehri but I did not make the intention to fast as I was worried whether the fever will worsen and that maybe I will need medication. I did not want to break my fast. However, during the day I feel I can manage until iftaar. Will my fast count or I will have to replace it?