I have troubles with pepper plants. I have a few this year and they also don't look like they are doing anything. BUT one of them I put one of those water cooler tanks (clear blueish 5 gallon jug) that had the bottom cut out over top of it and even though it didn't grow taller it did create a nice almost bush looking plant and started to flower. So I took it off so the bees could do there thing. I'm thinking about doing the same for the other 3 plants. I was told they like the heat so I thought I would try it with one of them. Oh and make sure you leave the top hole open otherwise you will cook the plant.
Those jugs worked great for my tomatoes earlier this year. They when nuts even when it wasn't quite warm enough for them to be outside. The are much larger and nicer looking this year compared to last.