Right, for a start any weight you lose through using a laxative is going to be water and/or bowel contents. It gives you the illusion that you are losing weight, when in fact you aren't actually losing fat. COMPLETE WASTE OF MONEY. While they may not be inherently bad they have little if any benefit.
Secondly EAT MORE FRUIT AND VEG, it is high in fibre which will naturally make you more regular, plus there's all the added vits and minerals, it will make you feel much better. Aim for at least 5 portions a day, ideally 10. If you're constipated chances are that it is diet related (ie; too much protein, very little fruit and veg, etc), a herbal laxative is a short term solution but it will not treat the cause of the problems (ie; you not eating properly).