It seems like your client isn't properly synced. A rescan should fix this.
First, did you already create a backup of your wallet.dat ? If not, immediately do one!
Second, if you don't necessarily want to use core, you might simply use a lightweight client (e.g.
electrum).
You can export your private keys from core and import them into electrum. Since electrum is a lightweight client you don't need the whole blockchain stored.
For your next transaction pick a slightly higher fee. Or, if you have time, 1 sat/B should be fine (which could take longer to confirm).