Well done on your weight loss Bibiana - 3 and 1/2lbs is a great start but you have probably lost alot more than this because your weight fluctuates by up to 2 and 1/2lbs during the day - that's why they say you should weight in at the same time of day. I'm always loads lighter in the morning than the evening.
With regards to your other problem I suffered at the start and actually used laxatives for a couple of weeks (which I don't recommend) because I was in agony! I now take 2 spoons of 'Benefiber' twice a day; it is a powder, has no taste, no colour and can be mixed in any drink apart from a carbonated one. Its not a laxative but a soluble fibre food supplement. It took a good week to 10 days for it to work but now I don't suffer from constipation, wind or stomach cramps and I am regular every day. You can get it from Boots and Tesco (but not Rowlands chemist unfortunately). I put it in my morning shake!
Keep up the good work.