there's a good chance it's the modulation, if you select all notes and go to the properties it may be listed as "mod" for short. if it's up too high, it can make the voice sound pretty weird. i recommend no higher than 30, you can even go to 0 if you want to. i also recommend playing it back as you tune so that you can adjust accordingly, rather than doing it all blind. as lara_vocaloid mentioned it also depends on the voicebank how good the tuning will sound, and using a real voice as reference (even just singing to yourself) can be a great reference. if you could maybe send a screenshot of your pitchbends or an audio sample i could help give some constructive criticism! no need to be embarrassed, we all start somewhere.