28 weeks pregnant HELP

Lauren

I woke up this morning felt fine as the day has went on I felt nauseous but haven’t puked but when I get this nauseous feeling my stomach tightens and hurts.. I’ve had a lot more discharge today and some back pain I went to have an ultra sound on the 21st of this month and she said baby was head down could I just be getting sick or should I worry the nausea comes and goes like contractions .. thanks