Sudden fear of cold water

Hi everyone!
I'd like to share something with you all. I've been with my boyfriend for 5.5 years, we've been living together for 3.5 years, and we're very happy. Over the past year, we've talked a lot about wanting kids. I couldn't think of anything else. I really wanted a baby, preferably yesterday. My boyfriend is also very enthusiastic about it and wants nothing more than a baby. I'm still studying, though, so that's been getting in the way a lot.
Now we've come up with a plan that works for us, so we can start trying next July! We're really excited about it and looking forward to it. My boyfriend can handle this pretty well until then, but it seems like I'm not thinking about anything else. I'm constantly thinking about it (is this relatable?) while telling myself: 'Take it easy, it's still a little while away, just enjoy the moments now.' But lately, I've started worrying a bit: 'What if having a baby isn't as fun as expected? What if our relationship becomes less enjoyable? What if I regret not waiting longer? What if I can't handle being a mother? What if my body becomes really ugly and my boyfriend no longer finds me attractive? What if I can't handle the birth?'
I really don't understand where these thoughts are coming from all of a sudden because I (we) have thought about this seriously for a long time. It's really not an impulsive decision, and the foundation is so good for a baby. I feel a bit confused by all these thoughts, and I was wondering... do other mothers/expecting mothers here have experience with this and/or have had issues with it?
Thanks for letting me share this, and I look forward to your responses! Love,