Crackling sound r nothing but crepitations in knee joint. Take wax bath, short wave diathermy and ultrasonic massage for knees regularly for 21 days at your nearby physiotherapy centre. Continue quadriceps exercises. Avoid painkillers.
No you are not pregnant
There is no fixed time in which one bleeds after taking ipill. Sometimes unexpected bleeding occurs more over it is not necessary. Next menstrual cycle can be early or delayed as side effects of the pill. As she has taken within 24 hrs it is 95% effective.
Meet a Physiotheripst to get assessed and they would tell wat needs to be done according to the assessment result. Lower back stregthening exercises helps in preventing the spine from any injury further.
Use flat bed or ortho bed available in market. Prolong sitting will make your pain worse. Take a break after sitting 15-20 minutes. Do regular streching for your back n neck muscles.
Avoid bending work. Try to sit straight ad possible as .your whole back should be supported by chair. You can put cushoins behind your back while sitting. Take back support while driving.