No, you're not worrying too much. I work for the local Health Dept. in a program for moms & babies. We do routine developmental screens and putting weight on legs is one of the things we look at around 6 months. (Maybe earlier-- I do a different job now and I rarely do the screens, but I do remember that that particular item was at 3 or 6 months.)
I recommend that you talk with your pediatrician and request a development screen. (I recommend the Denver Development Screen, it is pretty thorough, well-tested, and most doctors & nurses know how to complete it.)
If you are in Indiana, I also suggest that you look into First Steps. That is the organization that helps identify and treat early developmental delays. Most can be corrected with just a few months of therapy. Services are covered by most insurances & Medicaid and First Steps will not turn a child away because of a family's inability to pay. They do home visits and work around the family's schedule. I love their program!! Your doctor should have their phone number.
Yes, worrying is sometimes a good thing, but try not to stress too much over this. I have seen lots of babies with similar issues and all of them recovered and were caught up with their peers within 1- 1 1/2 years.