Painfull right leg on right hand side. Started three days ago after walking in the morning about a mile.?

My right leg went very painfull and every time i tied to put any pressure on it it was very painfull and i could not move. THis happened all afternoon untill i went to bed. Now its ok when im not doing anything or just pottering around my house but as soon as i start walking outside on my daily walks it starts to go again.The pain i get starts at the side of my knee and goes all the way up to my bum it feels very tight and then seems to start sprading all the way down my leg and up my side. I should state i had my second child by c section 3 weeks ago. I have started putting back on my stockings to prevent dvt as im a anxious person and am worrying also the presure stockings seem to help ease the pai. Ay ideas as to what it could be and should i worry about dvt.