Blossom drop, where the plant drops the blossoms without setting fruit, can be a reaction to a number of kinds of stress. Type blossom drop into the search box at upper left of most pages to find a lot more information about it.
Peppers are full sun plants, difficult to grow indoors without added light. If your window doesn't get at least 6 hrs of light, it's probably not enough. But if this is the case, your plant would likely be getting tall and leggy ( a little spindly as it stretches to find more light).
If it's a pollination issue, it might help to just gently shake the plant every few days to help with this. It shouldn't need more than that.