Hi Annbe
I am so sorry you find yourself on this forum, it really is every woman's nightmare isn't it?
I'm further along the road than you - I lost my boy at 16/17 weeks 5 months ago now. I can tell you that dwelling is totally understandable and acceptable. I can honestly say that there was nothing else in my head for the last 5 months but I am now starting to move on a little. My husband on the other hand is finding it very hard now (I would have been due on Saturday)and I really do believe it's because he took the 'mans way' of not thinking about it, not dwelling etc. so hasn't processed his grief properly.
Grief is a very personal thing and I don't think you can really make people understand, only you understand how you feel. I truly believe that you must go with whatever you are feeling at the time, your body/mind whatever knows what it needs to do to get itself through this (that sounds a bit weird but I hope you know what I mean)
I personally found it very hard as people didn't acknowledge what had happened, nothing was really said by anyone - I know it's because people just have no idea what to say but it made me want to scream.
The thing I found very helpful was writing everything down - I have Book (yes I actually have named him Book) and I write everything down that I'm feeling in Book. If anyone read it, they'd think I was complete fruitcake but I find it a very effective way of spewing all the crap that's in my head without anyone having to think I'm a nutter or burden anyone with my thoughts. The great thing about Book is he never feels the need to give me an opinion, I can say anything to Book and it's unburdened me and it never gets brought up again - nothing worse than people remembering the nutty things you've said in the past 
Okay so I have now written on a public forum that I'm a nutter who talks to a book but I really would highly reccommend it - I've been in some very dark places over the last few months and I found it really, really helped to just unload it on a page - to the point that I do feel I am starting to move on.
Never feel guilty for 'dwelling' you've been through something horrendous that unless they've been there, people have no idea what it does to you.
Be kind to yourself, take care and if you need to cry, thump pillows or whatever then do it!
Anyway 'Nutter' is going to stop waffling now and hey maybe I'll go and talk to 'Book' 