It fits it's a size 8

So recently I have been noticing something rather annoying in shops, that is the sizing of clothes. I was in a shop and tried something on in my usual size 12 and it was far too small and I actually had to check the tag to see if they has put the wrong tag on, but no it clearly said size 12, so I thought oh we'll il just try the 14 on and that was still too small! Refusing to settle for a size 16 I walked out the shop feeling huge and my confidence trampled on, I felt awful. I went to another shop another time and tried on a size 12 top and it was all baggy so i looked for a size 10 but there wasn't one only an 8, I thought that it would never fit but it actually fitted fine! I couldn't believe I was wearing a size 8 top, so I bought it straight away and left with a smile on my face The next time I went shopping I tried a dress on in a 12 and it was too small so I had to get a 14, another shop I bought a size 10 top and another shop I bought some size 14 shorts, this was just getting stupid, how can the sizing be so different? I decided to look at clothes online and so I looked at the online size chart, I was horrified when one particular website said I would need a size 16 when another website said I would need a 12, the amount of times I've bought clothes online and had to buy one in each size as they are always different, it was becoming a guessing game rather than knowing what size you are and ordering it. If I had something in a 16 I would cut the label out as I would feel embarrassed wearing this size! It made be feel like I'd put on loads of weight but really it was the clothes. When did sizing in shops become like this, I mean who actually decided on the sizing or do they just make it up, literally every shop is different it's ridiculous, then there is another issue and that is bras!! I range between about 3 sizes in every shop, why can't every brand use the same system! Xoxo