It's a major change in your life, you are entitled to feel however you feel about it.
My partner and I were trying to concieve for 6 years. I spent most of last year losing weight to try and get myself healthier to help us have a baby.
When I found out I was pregnant as well as being happy that we could concieve, I also felt complete disbelief and when it sunk in that it was happening, anxiety. I just hadn't really expected to get pregnant, and I was worried that I wasn't ready, my body wasn't healthy enough, our finances weren't good enough, that our home isn't good enough, that there was stuff I wanted to achieve before I became a mum etc.
So it can be really scary getting pregnant and realising that 'this is it' that you are less than nine months away from a deadline to be 'ready' for a baby - and that's even if it was what you planned and hoped for a baby for years.
I can't imagine how it must be when the pregnancy wasn't planned, but please don't think that those of us who did plan it were perfectly prepared and only full of positive emotions.
I'm 17 weeks now and although I'm still overwhelmed at how much I need to do before the baby arrives, I am so glad that it is coming and I realise that I'm better prepared than I thought.
Do find someone to talk to about your feelings. Being apprehensive about becoming a mum is completely normal and doesn't mean that you won't be a great one! As soon as any big change happens in our lives (for better or worse) we sometimes need to grieve a little for the old picture we had in our heads about how our lives were going to go. Then we need to think about the goals we had, work out whether they are what we want any more, and we do then we need to find a different way of achieving them.
Parents still go on holidays, have careers, enjoy hobbies etc. They just need to work them around their children. Your life hasn't ended, it's just going to be different.