I have about 4000 pictures on my sd card but on my galaxy S4 it's only showing about 1000 not including the pictures I've taken since I got the phone. I really need to get this fixed because most of those pictures are of my daughter.
"I really need to get this fixed because most of those pictures are of my daughter"
First thing you need to do in that case is copy all of them to at least one hard drive or to optical discs if they are irreplaceable and valuable to you, then worry about sorting out the problem with your phone.
If the card becomes corrupted or whatever, and you haven't got the pics backed up anywhere, you risk losing all of them, so you need to get your priorities in the right order - - backups first! Memory cards can fail without warning at any time.
I'm surprised (even shocked) you haven't already backed them up before now. It's a disaster waiting to happen.
I agree with Phillip, that you need to back up your photos that are irreplaceable, but make sure your put the flash drive or portable hard drive in a place that doesn't get vibrated, such as a safe. Although, I would suggest putting them onto a CD and putting that in a safe place because I have yet to see a CD fail from using it.
Now to try and solve the problem that you are having.
Are you sure that all of the pictures that you have, your phone will recognize them?
If so then one of two things may have happened. Your files are unfortunately corrupt or the phone is having a problem showing all of the photos.
Have you had that SD in a different phone, such as an IPhone? If so then the pictures you had taken with it may be a different file type and is possibly the reason they are not showing?