Hey, I just signed up for this forum - as such this is my first post.
Like you, I recently played this game. Very recently - I downloaded it on Wednesday, I think? I just finished it last night (95%, all girls complete, just missing a few bad ends / art pieces).
Also, like you, I was a little scared after finishing one route that I wouldn't want to do the other routes. Some of the posts I've come across during my short time lurking here have been to give it a day or two between playthroughs, just to let the initial impression sink in and start to weigh a little less heavy on your conscience. These are, after all, characters in the same general story, so going right from one girl to another might trick your mind into thinking you're doing something wrong. But please, please don't pass up the other stories. They're absolutely phenomenal.
I also wanted to comment about your emotional feelings (commonly referred to as "feels", as it is difficult to hold them all). I'm immensely impressed and somewhat shocked at how much of an impact this game is having on many people's lives. In nearly all cases, it's for the better - people are making changes in their lives, reevaluating their relationships with friends and loved ones, exercising more, improving their knowledge of the disabled or even donating money or time to altruistic organizations. Granted, there are many posts I've seen where people are shaken up by the stories in Katawa Shoujo, but, as Hisao would say, "It can't be helped." - mediums such as this don't typically carry with them the emotional weight that this game carries, and it causes you to really think over your own life at the end. In my opinion, that's absolutely wonderful.
So you say that you feel that your life is boring and you are lonely... well, what steps can you take to alter that? The most important part of change is identifying what must be changed in the first place. Are you overweight? I am. Grossly overweight, in fact, but this game (in addition to a few other stimuli that occurred at about the same time in my life) have caused me to begin making sweeping changes to my habits. I've officially started a diet and exercise program which has been going absolutely wonderfully so far - I feel really amazing after my work-outs, despite being relatively low-impact due to my current condition. But it's a start, and it's already having an effect.
Are you shy? You can learn to overcome this hurdle, but the support of friends can be an incredible boon. Playing through Hanako's path can give you a little insight, and maybe some motivation to change this. Do you have some sort of personality disorder that causes problems with social contact? There are numerous organizations, most completely free to utilize, that can assist you in overcoming your fears and begin repairing your life to a point that you can operate at least close to normally.
At the end of the day, just know that you have the power within yourself to change. One of the main lessons that can be learned from Katawa Shoujo is that no matter how deep the flaw, it can be overcome. Regardless of whether it was your fault, someone else's fault, or no one's fault at all - fighting through your problems makes you a stronger, better person in the end. Everyone can achieve greatness, but you can achieve nothing if you never try.
I hope this helps, and best of luck to you.
Diet / Exercise Tracker:
Original weight (1/1/12): 400 lbs. // Target weight: ??? lbs. // Current (1/28/13): 344 lbs. // Total lost: 56 lbs.
Current exercise: Workout 3-4x a week: jogging, weights
"Hope is a good thing, maybe the best of things, and no good thing ever dies." - Andy Dufresne, "The Shawshank Redemption"