Hello and welcome to HCM.
Thank you for your query.
Yes, it is still considered normal to bleed 3 months after 
vaginal delivery, although not very common. 
In practice, we come across wide variations. Some women bleed with or without sexual penetration for 2-5 days, some continue bleeding even without intercourse for 2-3 months. As you have been experiencing a bleed only after intercourse, it is normal for now. This bleed is as your body is still adjusting to the change, and trying to return back to normal. Do not worry.
But, I would still advise you to visit your doctor and keep him/her in the loop. Go in for regular follow ups with your doctor for at least 6 months post-partum. I am sure this is normal, but it is better to be safe than sorry.
I hope I have succeeded in providing the information you were looking for. Please feel free to write back to me for any further clarifications. I would gladly help you.
Best wishes.