Hi there!  Congrats on completing your pants pattern!  Don’t worry about doing adjustments as this is a perfectly normal part of the process.  The basic pants are meant to be loose in the legs and definitely looks better once you press the middle crease in them.  How is the fit at the knees?  Also, when you sewed the front and back together at the side and inner seams, did the seams match perfectly?  I’ve never had bagginess in that particular area before but it might be solved if we shave off a little of the back’s side seams in just that area.  When you wear them, pin the back near the side seam and inner seam in your trouble area on just one leg, while wearing them.  (I definitely have a friend help with this part.)  Compare the two different legs and see if you like the fit better.  If you’re liking it, remove the basting stitches and resew, taking your pin marks into account.  Just make sure to always sew a smooth line so we don’t create problems in other areas.  If you like it, transfer the changes to your draft.   Since these is your own personal pattern, we can make small tweaks and this should have no affect on the grainline.