Lack of weight gain

Lets start with the weekend.
Saturday me and hubby managed to get a lay in, out little boy slept in a bit longer then usual which was great. We did the last of our Christmas shopping, so apart from secret santa we're all done.
secret santa is something we started doing this year. I'm hoping we'll do it every year. I got my brother-in-law (sister-in-law's hubby) he's pretty hard to buy for, this year it's joke themed. He doesn't take jokes very well. He's quite a stressed person so thought about getting him booby stress balls. Then thought well he hates people touching him so I could get him something that say I need a hug on it, quite a few ideas have gone through my head.

Sunday I went to see my dad and step-mum as it had been a few weeks since I last seen them. Spent about an hour there, talking about general chit chat and what time we'll be over Christmas day. We had sunday dinner over hubby's parents. Little one had his first roast not mashed up, he did pretty well with it.

Today
Well I got the fright of my life this morning, half asleep and all I hear is a thud thud and then a cry. Go running  into my little boys room and he had fallen out of his cot. I have no idea what the hell he was trying to get, but it must have been something as usually he's pretty good in his cot and won't lean over in it.
He was sick about 10 minutes after which scared me, I didn't really want to let him nap, but thought I'm pretty sure I read somewhere it was ok for them to sleep as long as you can wake them up. I thought ok i'll let him have his nap and then if he hasn't woken after 2 hours then i'll try waking him. Luckily he woke up just before the 2 hour mark.
He seems normal in himself which is great. But now he's teething. I think his top teeth are coming through, or one of his back ones.

I phoned my health visitor today to see if I could change my appointment as its for me any where. It was meant to be on the 19th but hubby can't get the time off work so I tried changing it to the Monday after. but they not open then. So now they are coming to me Wednesday instead. I explained that I find it hard to leave the house on my own, and they were more then happy to send someone to me.

Ok so now to today's topic.
Lack of weight gain.
Weight gain is a worry for quite a few pregnant ladies. With my last pregnancy I struggled to gain the weight, gained 15lbs in total 10lbs under the lowest recommend weight gain, and my son turned out to be a tiny baby, an IUGR baby.
Now I am a little over 28 weeks and have gained 9lbs. It makes me worry that this baby will also end up being an IUGR baby. I read that lack of weight gain can cause it. The problem is I am eating. I've never been a big eater. I'm not eating less so surly I should be putting the weight on.
I know it means less to lose when I've had the baby, and your probably thinking what you moaning about you jamming bitch I've gained like 20lbs. But having read that lack of weight gain can cause IUGR has mad me think it's my fault that my son was so small, and if this baby has it as well its going to make me feel worse about. I think though I will ask if it's my fault this time. All I was told last time was it's because I am small (5ft) which I can't help. So if the reason was because I am small, would that mean my baby will have IUGR like my first did?