What strength pen will you be using? I did shoot up weekly from 5 to 5.5 to 6 to 6.25, but in hindsight might have slowed down.
I now tend to go up in much smaller increments, by just a few clicks every week or maybe by 0.2mg after 3 or 4 weeks at one dose. However, my weightloss is currently progressing, so I can take it slowly again.
But, if you are week 28 or so and aren't getting the desired weight loss effect, maybe you need to increase your dose a little more towards the next standard dose?
In your position, I would increase to 5.5mg for the next shot and see what happens. If ok, stay there a couple of weeks, or go up a bit to 5.6/5.7/5.8 the following week.
You've been on MJ for a long time now, so should be tolerating the med better than earlier in your journey and should have 7.5mg in your sights, if this would give you the weight loss you desire.
I just don't see what you gain from staying on a low dose for a very long time if it isn't really working for you. I know many people say they never moved up from 2.5mg or 5mg, but not everyone is that lucky. Also, some say very proudly that they "only take 5mg", but later admit that they take it twice a week!
We are all different. MJ isn't magic, so taking only a partial dose doesn't always let it support us effectively in our difficult journeys. As always though, discussing with your prescriber is the best option, as we aren't experts.