iCloud Storage

I have been getting messages that my iCloud storage is almost full. I still, after 6 years, have only needed the free 5GB, having used until recently only about 3.5GB. Suddenly I'm alerted I have used 4.9GB. I deleted a ton of photos, all text messages but a handful, and lots of emails. It fell back down to about 3.5. Yesterday I was alerted again and today it says I have reached my max of 5GB. What is happening and how can I fix this? I haven't added anything but a couple of photos.