When I try to back up my phone it says I don’t have enough storage but when I look at my storage it says that 155.1 MB of 5 GB is being used I cannot backup my phone.

Your iPhone needs more than 5GB of free storage space to complete the backup on iCloud. You have the 5G option for iCloud and your iPhone needs more than that. Your iPhone backed up what it could in full however there are other files that couldn't be backed up due to limited space on iCloud.

Axel F.