I say breathe....
If you don't have to take something for losing weight, then don't as it really can mess with your system. Getting your hormones in check with the right birth control will do wonders too. All that on your plate will totally make you irratable. Taking Vitamin B every day will totally relieve PMS symptoms as I have found out myself personally. You have to take it for a good three weeks before you see the effects but it helps.
Go get teething tablets for your son, it helps a ton!!!
Instead of taking something for weight loss, try green tea, cutting just 300 calories out of your diet a day and not eating after 6:00pm...you will be amazed how it can drop off without any medical intervention!!!!!!!!!!
Taking time out for yourself is crucial too.
Keep the lines open with your hubby, explaining you aren't angry with him but will work on being better at not snapping at him. Making sure you take responsibility for your actions.
You are young, you will lose the weight without meds, promise, you just need to get your body on the right path.
Women take a good year to get their bodies, hormones back after giving birth too, so give yourself a break.
Talk to your Dr too as you can have Post Partum even mos after a baby is born....
Hang in there, breathe, take time out for yourself (a bubble bath), take vitamins, go for walks with your son, drink green tea and talk to your Dr!!!!!!!!
Hugs.