hello there..

Amoxacillin belongs to penicillin group of antibiotics and is definitely safe in pregnancy. It is most commonly used antibiotic to treat infections in pregnancy. Also Robitussin contains guaifenesin which is safe in pregnancy. So you can continue these without tension more because they are improving your cough.
Besides these you should keep taking your folic acid tablet daily which is routinely advised in pregnancy and help in proper development of baby without any structural defects.
Also to improve your cough keep doin warm saline gargles along. Warm, salt-water gargles draw out the mucus and reduce the painful swelling in the throat. Salt also quells the itching sensation in the throat. Gargles with warm water mixed with lemon juice and honey are equally effective.
Suck a slice of lemon with salt and black pepper on it to reduce the intensity of cough.

Hi welcome to Health care magic forum . You had respiratory tract infection and it is transforming into lower respiratory tract infection , that is why the phlegm is greenish and there is difficulty in breathing. As you are still in 7 weeks pregnancy catagiry drugs should be used as far as possible. Of course if the infection is more other drugs also must be used .
Besides i advise you to follow some diet recommendations as Avoid taking fruits, juices, sweets, cool drinks, ice water, ice cream, brinjal, and fish. till you get complete relief from the symptoms.
Take more of green leafy vegetables, pulses, sprouts, milk, egg, meat, and dry fruits to increase the blood, general health necessory for healthy grouth of the baby, and resistance to such infections. Wishing for a quick recovery , ands thanks for calling.