Hey, the first thing is, well done for identifying this as something that needs to change. Alcohol impacts everyone differently because there are so many factors involved - everything from how much water you've had to drink to your body size to your personality to your mood can have an impact on how you react to alcohol, so it's really impossible to predict what your reaction is going to be. In all honesty, though, a lot of people don't become nicer when they're drunk - I do have friends who just become sweet and funny when they drink, but I have equally as many who (as someone who chooses not to drink most of the time) I have to tell off for being unkind or inappropriate when they're drunk. It's not just you by any means.
The first thing to work out is what your goal is - are you aiming to cut alcohol out, or to reduce the amount you drink to a level when you're in more control of yourself. If it's the former, then that's easier to work out. If it's the latter, try working out how many drinks (and then howsny units of alcohol) it takes for you to become a person you don't like. Compare that amount to the recommended weekly intake limit and work out a new limit for yourself, for example, you might choose to half the amount you drink in one go. The trick is to make sure it's an amount where you'll be in control of yourself to actually stop when you get there. For this reason it might be easier, at least at first, not to drink at all until you're used to it feeling ok not to drink just because other people are.
The next step is putting it into practice. I've found that people are always really nice about me not drinking. One thing is that most people use alcohol as a disinhibitor to make them more comfortable socialising. What they don't really is that alcohol is a depressant and (as people do realise!) Never makes you feel better the morning after. But when you're spending time with people who are drinking, you can bounce of their moods to help yourself feel more relaxed and comfortable socialising. It's not exactly the same, but I find that doing this means I have as much fun when I don't drink, or to be honest probably more, than when I don't drink, and then I can remember what happened and have memories with my friends to keep. And then you don't have to worry about becoming a person you don't want to be when it gets to a certain point in the evening.
Next, find things you want to drink instead. I really like mocktails, but also fruit in water tastes surprisingly like Pimm's. If you have a 'drink' in your hand then no one can tell whether it has alcohol or not, so if you're nervous about peer pressure or judgement then this can really help. I also really like it because a lot of mocktails taste really nice and J don't have to worry about how fast I drink or how many I have. But honestly people are usually really nice about it - in my first year at uni my friends would always get digestive biscuits for me to use when we played drinking games instead of alcohol I don't know why it was biscuits but it was very sweet if them anyway!
So that's how to cope with being with friends who do drink, but naturally there are a lot of people in the world who don't drink, and a lot of places where people who do drink won't drink. Sometimes it's nice to have hobbies where people are unlikely to drink, so you know you can spend time with friends every week where it won't be a worry. So if you don't have any of these yet, try out some different clubs and societies and see if you like anything. Some societies will include after sport drinking, for example, but a lot of even most won't
If you have any other questions then feel free to ask. You're taking a big step but the hardest bit is recognising that it needs to be taken, so you're doing so so well.