Sorry for your frustration.  Sounds like you need to do focused drills on chord changes until they are second nature.  The time it takes varies by individual student.  But the same thing has to happen.  You have to do enough repetitious practice on any given physical motion until it becomes completely automated.  Organize your open chords into groups & drill them as changes.  Don't strum them in time, don't play them as a song.  Do this:

Play one chord (C major, for example), strum it once to make sure you've got it sounding good.  Stop.

Play a different chord (G major, for example), again, strum it once to make sure you've got it sounding good.  Stop.

Repeat.

Do that for an entire practice session.  Do that mixing & matching all the open chords you know.

Until you can do those changes smoothly & naturally you aren't going to be able to play them in time in a song.  After you can play those changes quickly & smoothly, then you can start to work on strumming them in time to play a song. 

"All i hear around me is that you should keep practise sessions short, but frequent and that's what I've been doing really."

How short?  That strategy is fine as long as you are getting enough repetitious practice to automate the physical motions.  Practicing an hour is better than 10 minutes.  Especially if you are practicing effectively.  Playing more is always better than less, as long as you avoid physical injury.

"After everything that I just said, it may sound crazy, but what do you guys thing about buyng an electric guitar in this situation?"

Playing an electric guitar is often easier because of the smaller size, lighter strings & lower action.  But it's not going to replace hours of repetitious practice.  :)  That part is required regardless of the instrument you play.  Go to a local music store & try a bunch of guitars to see which one is affordable & feels good in your hands.

Hope that helps!