I've had this phone for two years so all my photos are saved on the actual phone (not a micro SD card). I'm wondering if I reset it, will I lose all the photos saved on my phone? I'm not bothered about losing the apps just my photos I'm concerned about.
That very much depends on a) where exactly the photos are stored, and b) how the factory-reset is implemented on the device. As you can find out via the factory-reset tag's tag wiki (just hover your mouse over a tag and select the 'info' link to access its wiki), a factory reset will remove all your data and the apps you've installed. It usually does not touch the SDCard (external or internal).
Still: if you have the possibility (and your question does not seem to imply trouble booting your device into normal mode), why not copying everything you are concerned about (and which you can access) to another device, such as your computer, before doing the factory-reset? With that, you would be on the safe side.
Maybe. It's probably safest to just back them up to the cloud or an external device. Google Photos is an easy way to do that.
Everything will be erased.
While each device may handle a factory reset differently, they are meant to do just that, return the device to how it was when it came from the factory. This usually means deleting all data on the device, including apps, musics, photos, downloads, etc. Some device may not automatically erase an SD card, instead providing you an option to do so, but other may do it without warning.
The safest, and most advisable route is to back up any and all data you do not want to lose before any reset. There are many free services available for backing up photos (Google Photos, DropBox, etc.), or you could connect your device to your PC and copy the photos manually.