Lot of pregnancy symptoms on 2nd depo shot such as nausea i always feel on the verge of throwing up, off and on brown discharge but regular discharge too, sore breasts, hard nipples, lower back pain, abdominal cramps, sharp stomach pains, feel weak??

Hard to guess: It can be hard to guess whether a woman is pregnant or not. A urine pregnancy test gives a very reliable result by 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period, or after having a "weird" period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon. Depo-Provera works well.