You can try to recover your Photos. The best way is from a computer. On a computer, sign in to iCloud.com using Safari and your Apple ID. Then, click on Photos. Near the left top on your screen you'll see Recently Deleted. Click this tab and you'll see which photos can be recovered. If you select one or more of them, a Recover tab will appear. Click it and the selected photos will be restored to iCloud.
FYI, you can back up your phone on iCloud or a computer. I always backup on a computer because everything on my phone will be backed up and can be restored with virtual certainty. I can't say that about backing up a phone to iCloud. Please see this read About backups for iPhone, iPad, and iPod touch https://support.apple.com/en-us/HT204136 It covers backing up to a computer and to iCloud.