Horsey What you are feeling isn't 'normal', but you aren't alone in feeling that way. I can empathise with the way you feel.
It is a massive massive life change. To go from having only yourself to look after and think about, to suddenly a whole new person (who lets face it, don't exactly make the process easy, do they!) to do everything for. I don't think it would be normal to not have anxiety or worries over this.
Motherhood (for want of a better word - crap description!) is one of the biggest life events, a massive shift in the direction of your life. We don't recognise this enough. We don't realise how hard it is - emotionally!
You know if you did want to go back to work - you can. But it might be worth talking things through with someone face to face first. Working through what is making you feel that way? Seeing if there is anything you can try to help you adjust smoothly.
But if going back to work is something which would help you, don't feel you can't. Some people function better this way. A lot of parents go back earlier than the 6/9/12 months maternity leave.
Be easy on yourself, you are allowed to feel whatever you feel - don't feel it is wrong. Please do go and talk to your health visitor, or GP, or just someone you are comfortable talking to about how you feel.