Hi hun,
Awwwwww try not to worry!!!
Thers is 16 months between me and my sister and my Mum said that she really didn't notice it being hard work, in fact as my sister got a little bit older (she was the youngest) that I was a help as I helped her to advance and wanted to spend lots of time with her, so I entertained her and stopped her crying as much as she may have done had I not been there - we are also close which is lovely!
AND my sister is following in my Mum's footsteps with having a 9 month old and she is 14 weeks PG again!
So look on the brighter side it may be harder at first, but fingers crossed it will only be initially!
Good Luck babe, and I hope you have a very healthy and enjoyable pregnancy!
Tam x