It is possible to feel some fluttering or movement in your belly at 12 weeks pregnant, but it is unlikely to be your baby's movements. At this stage, the baby is still very small and their movements are not usually strong enough to be felt by the mother. The sensations you are experiencing could be due to a variety of factors such as gas, bloating, or muscle twitches. As your pregnancy progresses, you will start feeling more distinct and noticeable movements from your baby. These movements usually become more pronounced around 18-25 weeks gestation. If you have any concerns about what you are feeling, it is always best to consult with your healthcare provider for reassurance and guidance.