It is very possible that you would qualify for free counselling to deal with drug and alcohol problems either through school or social service programs.  At the very least, I can tell you that AA meetings cost absolutely nothing.  And they help.
Please still think about these options for you and your baby.

Give your baby a chance to start out life as healthy as possible.....There are PLENTY of FREE services out there you can take advantage of. Start with AA. Folks there can point you in the right direction, all you have to do is ask......If your child is born with drug/alcohol related birth defects he/she WILL be taken away and you could be looking at crimal charges......Stop it NOW. Before it's too late for you both.

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Smoking marijuana during pregnancy may affect your baby's growth and the development of his nervous system. Studies have shown that children who were exposed to marijuana during pregnancy sometimes have problems focusing their attention and solving problems.

Children of heavy pot users may also have problems with short-term memory, concentration, and judgment. (There's no evidence so far, however, that marijuana use during pregnancy causes attention deficit hyperactivity disorder).

One study even found that young children whose mothers smoked marijuana during pregnancy had a higher risk of leukemia than those whose mothers did not.

What's more, there's no way to know if the pot you're smoking has been laced with other drugs (such as PCP) or contaminated with pesticides, which would put your baby at even higher risk. And using marijuana increases the chance that your baby will have birth defects if you're also drinking alcohol or smoking tobacco.

If you smoked pot before you realized you were pregnant, don't panic. The chance that your baby has been affected is very small. Still, it's important to be honest with your practitioner about your previous use of pot and other recreational drugs. She may want to run some extra tests to be sure your baby is developing normally.

~ Gerald Briggs, pharmacist clinical specialist

Fetal Alcohol Syndrom
Alcohol is capable of causing birth defects. This capability classifies it medically as a teratogen. Alcohol is now recognized as the leading teratogen to which the fetus is likely to be exposed. This applies only to societies in which alcoholic beverages are consumed. In these populations, prenatal alcohol exposure is thought to be the most common cause of mental retardation............

http://www.medicinenet.com/fetal_alcohol_syndrome/article.htm