Hi J.,
I had my daughter on May 9th, and have nearly the exact same problem. I have been pumping/nursing, taking fenugreek and another lactation blend supplement capsules, then finally Reglan. My supply has only barely increased, and not enough to satisfy my baby. I didn't want to give my girl formula, but she wasn't gaining weight, so I had to. The important thing to remember is that you are doing the best you can, and don't let ANYBODY (friends, family, strangers OR lactation nurses) make you feel bad. We are not in a 3rd world country, and you do what you have to to make sure your baby is healthy and well-fed. Also remember, ANY breast milk is better than none at all.
My daughter also has a short frenulum. I use nipple sheilds to help her out because she just gets frustrated w/o them. However both my pediatrician and an ENT specialist recommended against clipping her tongue. Her tongue can reach her gumline, and that's as far as it will need to reach for all adult pruposes (speaking, eating). And the frenulum can stretch over time, so it may extend farther as she grows. Both dr.s have 25+ years experience and both said they've never seen a child that NEEDED it done. That said, they both said if I wanted to have it done, the younger the better and it probably would do my child no harm, but it may not help her either. Things to consider prior to having it done is YOUR pain during breastfeeding, and her weight gain. If you are fine and she is getting enough breastmilk according to your Dr, then it may be unnecessary.
Go with your gut, and get as many opinions as you need. Good luck!