Hi, Thanks for posting your query. Firstly I congratulate for your first pregnancy.
The symptoms that you have mentioned, do not suggest a stomach infection, you are most probably suffering from morning sickness. It is usually seen in first pregnancy and more so it starts around 4-6 weeks of pregnancy and may continue till about 16 weeks, sometimes peak around 3rd month (12 weeks).
Usually it presents in the early hours, and reduces as the day progresses. In some cases, however, it may continue and present in the similar way all throughout the day. The exact cause for this is unknown, but high levels of the hormone HCG (human chorionic gonadotropin) which increases during pregnancy is attributed to the relaxation of lower oesophageal opening leading to reflux of stomach contents leading to vomitings.
This discomfort can be minimised by having small feeds at more frequent intervals and avoiding spicy and oily foods that precipitate the symptoms. It is advisable to consult your physician as soon as possible because the condition, if severe can cause more vomitings, dehydration and weight loss.
Hope this is of some help.