in reference to your title question ...

for some people this is called OCD (obsessive Compulsive Disorder)
for some people this is called a phobia
for some people this is called unconsciously wanting to have children/be a parent/ needing to parent oneself
for some people doing this is a result of poverty
for some people this is a grounding/comforting/tool
for some people this is a therapy exercise they have chosen to continue to do.
for some people this is normal
for some people....

my point is this can be just about any mental /physical/normal thing and reason.....

with in me this was a grounding/self nurturing tool that I chose to continue doing and it escolated during the months my wife and I were planning and after pregnancy. now I channel this urge into supplying my children with the things that they need...food clothing shelter, toys....

unfortunately we are unable to tell you why this is happening with in ....you. for that you will need to consult your own treatment providers...therefore my suggestion is if this continues to bother you talk with your treatment providers. they will be able to diagnose this problem and if needed help you to understand the hows/whys and what to do about it in a way that is best for you.