Jen the people treating have probably done you a big favour by putting you on insulin now. Even though 7 is not a big number you are only 23 weeks and havent even hit true insulin resistance yet. If you were say 30 weeks and getting a 7 they would most likely have responded differently. What they are in fact doing is heading off a certain upwards trend before it becomes a problem.
Pregnancy related insulin resistance just goes up and up and up between now and aprroximately 36 -38weeks and if they hadnt put you on insulin now that 7 would have been in the teens before too long. Diet alone will NOT successfully treat GD when it occurs this early in the pregnancy. I would be thanking your team for their forward thinking in reducing the long term risks to you and your baby....you will definitely feel better in yourself if you can avoid letting the sugars get any higher. pregnancy makes you feel tired and crappy as it is without high sugar levels making you feel even crappier.