I agree with Jaquta that unintentional weight loss of any kind is worth discussing with your doctor.
I would recommend discussing your weight loss with your doctor.
While the weight loss is rapid it is possible that it is due to an increase in activity levels and also the fact that the weight is there to lose. ??
I think for constipation, fibre, water and exercise are said to help.
I would talk to your doctor and let them decide what, if any, tests are appropriate.