urine drug test UK!

Does anyone on here know what way the urine drug testing works in the U.K. My health visitor referred me to social services over depression, to get me support, but I refused and disengaged so my kids ended up on child protection register. Since then, things had got sooo much better, I was almost rid of them, and me and my social worker get along good, she knows my kids are happy and healthy and well looked after etc. And until now there was never a single concern. BUT, I let an old friend back into my life, and confessed that while I'm now pregnant with my 3rd child, I've been smoking weed. Suddenly it was reported to social services and my social worker had me tested. I have no idea how long it's going to take to get the results back. She give me the opportunity to admit it and I still lied. Even tho I know it's going to come out. I just got scared on the spot. And needed to buy myself any time I could. What is going to happen over this? Will they take my kids right away? Will I be given time to prove myself? And how long do results take? I'm due my baby at the end of August.