Lemon tree dropping loads of leaves since being brought inside is this normal?

[childminderjanet]

I have a lemon tree that I brought in about 2 weeks ago, since bringing it in it has started to drop quite a few leaves. I thought fair enough at first but it's showing no sign of slowing down. It's been fed watered(not to much) it's not overly hot in my back room it has plently of light. Any ideas where I'm going wrong I bought it in may so have never overwintered it before.
Thanks Janet