More than likely, your aches are your round ligaments getting bigger and pulling because of the weight of your uterus.  I have been having those aches since about 8 weeks (I'm 15 weeks today).  The butt pain is generally sciatica.  You can get it at any time past 8 weeks, but it's most prevalent in the second and third trimester.  Basically it's when something shifts and kinda sets on top of your sciatic nerve.  The pains start in your butt, and the worse they get, the further they can move (they can shoot from your butt, all the way down your legs).  I'm like you--I want to know about every single ache and stuff.  I was pregnant in 2009-2010, but I got a massive infection and went into preterm labor at 22 weeks, so now I basically call my doctor about everything.  Yep, I'm the annoying patient LOL!  I'm super excited though because we get another ultrasound on Monday!  (we've had two so far...when you go to a perinatologist, they are NO JOKE about the ultrasounds--you basically get them every time you go in!)  Fortunately, my husband works (and we live) on a college campus where the clinic has a CNP who used to be a midwife as well (she's getting ready to retire), so she has me come over to the clinic pretty much every day to listen to the heartbeat :-)

Hope you're doing well!

Lauren