Moms: joint pain & stiffness?

Lo • Jesus is the Way, the Truth and the Life :)
My baby is 6 months old and for the past few months I keep getting really bad joint/muscle pain & stiffness. 
I used to sit cross-legged all the time and get up no problem but now I feel like I'm about 90 when I try to stand up - it is SO sore and stiff!! 
My sister in law has an 8month old and my cousin has a 3 month old and they've had similar pains and stiffness. 
Just wanted to check if any of you guys have it and when does it go back to normal? (Please tell me it does!!)