The loss of height from compressed discs is most likely negligible even over the long term. Over the course of a normal day spinal discs will compress, but spring back during normal sleep. Even under high loads, the spinal discs will spring back relatively quickly - this being part of their primary function.
Regarding weight loss and height loss, I've never seen any research studying this. However, fat lose could cause a marginal (sub-centimetre) loss in height, however this would most likely be offset by a similar corresponding height increase caused by less body weight compressing the spine.
Either way, while I find it difficult to believe that weightlifting and weight loss could cause a measurable change in height, I couldn't find any evidence to back it up.
If you think you've gotten shorter, it may just be a change in posture. Pelvic tilt, which can be caused by poor posture or imbalanced training of either the anterior or posterior chain can cause a noticeable change in height, among other things.