my MIL asks how I am feeling and I told her I haven't been sleeping well because of pretty intense back pain... her response was "oh wait, it's going to get worse". 
BFP#1: 6.21.11 - DD born 3.6.12
BFP#2: 10.27.13 - Chemical Pregnancy
BFP#3: 5.27.14 - EDD 2.6.15 - MMC diagnosed at 8w3d - D&C 7.7.14
BFP#4: 1.9.15 - EDD 9.21.15 - Praying for a sticky bean!

Re: This really p!sses me off!
Started TTC 05.08
Me: Stage II endo, borderline high FSH
DH: perfect
1 lap, 5 IUIs = 4 BFNs and 1 c/p
2 IVFs, 2 FETs = 1 BFN, 1 c/p, 1 ectopic and finally a sticky BFP in May 2011!
1 FET in Aug 2013 = BFP!
I HATE those comments, no matter who they come from!
But I think it's even worse when they're from girls who are my age (19-20ish) and think that just because they've had ONE baby, that makes them an expert on pregnancy. It's so frustrating!
Same here... We've had a few scares during the pregnancy (Baby had a possible brain issue and we had to get fetal MRIs and all this craziness; I've been getting biweekly ultrasounds to monitor his situation... so far so good), but all the IL's know is that the pregnancy is going great and I have no problems at all! MIL tries to get more info out of me (even asking exactly how much weight I've gained - uhhh... enough) but I always deflect.
The other day, FIL said, Wow, this has been so easy for you, you should just keep having them! LOL.
I hate hate hate the "just you wait" comments! They're the worst!