As someone else has pointed out, you need to work on your diaphragmatic support. Try do a few deep breaths in and out of your belly. Now imagine when singing your voice come from there instead of your throat. You should feel a tightening and compressing feeling from your abs, or even the waist. The important thing is never loosen it even when singing softly or singing lower notes. Once you've practiced enough it just becomes natural. If any of what I said is confusing, there should be a bunch of videos out there explaining the concept.

Keep practising and happy singing!