For the past 4 to 5 months I have had large blood ...

When menstrual bleeding is heavy, clotting can also occur. Losing large clots can be extremely upsetting and even painful if they are large they can cause cramping as they pass through the cervix. All blood contains a clotting factor. To enable menstrual blood to flow freely from the uterus and leave your body without clotting, the uterus produces an anti-clotting agent. If the menstrual loss is heavy, it is possible that the anti-clotting agent will be used up before a period has finished, so that the remaining blood is likely to form clots.

Here is a site you can read more on as well, also make sure you check out the page " Investigating Heavy bleeding" Which lists some things your doctor could do to find out the cause for your heavy bleeding.

Read here

Hope this helps, If you need anything

I read the article but I do not have heavy bleeding my bleeding is normal sometimes light other then the clots .Sometimes I bleed for one day then I stop and a few days later I get my peroid and that is when the clots begin. I get the clots all the way to the end of my period. Should I be concerned?

Probably not, not since you are not bleeding heavy as well. But since this is something new as you say about the last 4-5 months, I would get some basic blood tests done to check your platelets, proteins & natural clotting factor. Just to make sure that it's only related to your menstruation. You doctor you saw knows your full medical history where as I don't. But since it's not something that has always been you may want to start with a blood test and go from there. It may just be hormone related as well. But with out some blood work would be hard to say for sure.

Hope this helps.