Looks like Mechanical Low backpain, though other causes can be ruled out only by clinical examination by an Orthopedic /Spine Surgeon. Treatment essentially is Medications, Physiotherapy and  Postural Care. Remember that besides wrong posture or weak back muscles, other causes also are possible so don't ignore meeting a doc and just relying only on painkillers available at the chemist or hot fomentation/ointment for relief.

Hot fermentation. Rest. Avoid strain. Tk soft pillow for back support. Posture correction must. Stretching exercises in gradually process. Avoid computer work. Tk few session of physiotherapy for better relief

In my opinion u need to go few sessions of physiotherapy... apart from this you need to do hot fermentation with spinal extension exs...bhujang asana...and some postural correction techniques at ur work place.. like you need to avoid sitting for long durations, avoid forward bending ,avoid lifting heavy weights, sitting should not be more than 30 mins... jst get up from your respective seat and again sit down...these are few posture technique which you can incooperate in ur daily life... take care get well soon...

Extension Exercises x 15 times x twice daily - lying on tummy, take left arm up for 3 seconds, then bring it down, right arm up for 3 seconds, bring down. Bring right leg up, hold for 3 seconds, bring it down. Then right leg up and hold for 3 seconds and bring it down. Repeat twice a day- 10 times.

Ensure that you maintain an appropriate posture while working or sitting or walking....Take frequent stretch breaks and drink lots of water...Discontinue using pillow while sleeping straight...Do not lift heavy objects, especially after bending down....Eat a healthy wholesome meal which should satisfy your minerals and proteins requirement...take over the counter pain medications.. Consult nearest orthopedic surgeon they will do the needful.

As per your complaints, It is picturising mechanical back pain means postural back pain. Combination of flexion-extension exercises can help alot. Postural guidance is crucial in your case.