That was brilliant. I just wanted to second the answer to you, coalminerswife. It sounds like it could be "situational" depression, as it's commonly called. As in, you've had something horrible happen and you are reacting to it, unfortunately we aren't always able to cope as well as we'd hope.
Again, medications should only be used if really necessary, and at that, only short term if that is the issue at hand. Get yourself to a good counsellor. I'm not sure where in the world you might be posting from, but this can get quite expensive to work through. So don't panic if you see the price-tag. There are many organisations (reputable ones) that will offer counselling at a reduced cost for those who may not be able to afford it - if that's an issue for you.
Also, if this is depression, just remember it won't disappear over night. Give the therapy time to work, and yourself to recover.
Lastly, you have the absolute right to look for a counsellor you like and trust. If the first one you meet with (and this is sometimes the case) doesn't quite "jive" with you, then meet another or two more, until you are actually comfortable. Otherwise, you may not keep with it, or completely follow the therapy.
I hope this helps some.
This is a horrible place to be in life - not enjoying it as you should.
I hope you get the help you need and feel better soon.
The symptoms you've listed (frustration at everything, wondering if you're "crazy", excessive tiredness, weight gain) occur in both disorders, but the difference between the two is that these are sufficient symptoms to be diagnosed with depression, but for bipolar you need a lot more symptoms of a very different kind as well. Also, bipolar is genetic and only triggered by environment (or possibly by the prescription of certain psychiatric drugs in childhood), whereas depression can be both genetic or entirely a reaction to circumstance (ie the loss of your boyfriend). So I'd say it's depression, in which case you should probably see a doctor who can refer you to a good counsellor to give you some coping mechanisms to help you through this and to prevent it happening again. If it ends up severe enough, you may also require drugs, but only go on those if you feel you really need them. Don't let a doctor just prescribe you drugs and turn you away again without some kind of talking therapy.