Chocolate doesn't actually have serotonin. It has a chemical called theobromine that is related to caffeine that is also a central nervous system stimulant and elevates our mood slightly (it's also what makes chocolate toxic to dogs), a chemical called anandamide that is related to THC and stimulates dopamine and the amino acid tryptophan that stimulates serotonin.
Chocolate can be healthy, it is packed with antioxitants, lowers blood pressure, lowers cholesterol, and makes us happy. It is the actual cacao that makes it healthy but it is expensive and without sugar too bitter for most people to eat. In the US chocolate can have as little as 10% cacao and still legally sold as chocolate and in the case of white chocolate it has none. Dark chocolates have the most cacao but in the US some dark chocolate can have less than 50% cacao. Better chocolates often put the percentage of cacao on the label. The higher the percentage the healthier the chocolate but since it has less sugar it is also more bitter. Personally I like 70% cacao dark chocolate the best; to me it is the right balance of strong chocolate flavor and sweetness. Some people find it too bitter and go for lower percentage and some people like the stronger chocolate flavor of higher percentages of cacao. My doctor even recommends that I eat a little strong dark chocolate daily.
Well chocolate contains serotonin which is a neurotransmitter in your brain that helps you feel happy. :) So, it's actually good for you when you're down and probably why you feel like you need it. Here are a list of other foods that have the same effect:
-dark chocolate (still chocolate I know but you may consider it healthier)
-Free range turkey
-wild fish and sea food
-high quality eggs
-free range beef
Some of the foods here may not be so appetising but give it a go :)
You can find other outlets to help you deal with sadness. For instance, you fight with your boyfriend-instead of sitting on the couch and eating chocolate, do something that soothes the pain and distracts you but doesn't come with the consequence of weight gain. Take a walk, ride a book, read a book, watch movies, etc.
when you have a craving for it, try to eat a fruit that is sweet, like strawberries or raspberries or a banana, after two to three weeks the intense cravings should pass, if you really need to eat it, get chunks of dark chocolate, it is much better for u and is actually somewhat healthy in moderation.
maybe instead of going for chocolate when you're sad maybe you should try journaling