I have a petite build and I love going to the gym. Will these implants look fake?

With ALL your requirements I would recommend Sientra textured implants as a better option. Discuss with your chosen PS. 

Thank you for the question and pictures. Base on your photographs, you are starting at a great place and should have a very nice outcome with breast augmentation surgery.  However, despite good intentions, online consultants will not be able to provide you with  meaningful specific advice.  Ultimately, in person consultation with well experienced board-certified plastic surgeons will be necessary. Careful measurements, dimensional planning, and careful communication will be key. Having said that, if you were my patient and looking for “natural look”, I would not offer you ultra high profile breast implants placed on top of the muscle. Regardless of your “working out" routine, I think that you will be best off having breast implants placed in the sub muscular position. The higher the profile breast implant, the more likely you will end up with an unnatural look. Make your decisions carefully…
Generally speaking, the best online advice I can give to ladies who are considering  breast augmentation surgery ( regarding breast implant size/profile selection) is:
 1. Concentrate on choosing your plastic surgeon carefully.  Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you're looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your   desired goals  with your plastic surgeon. This communication will be critical in determining which operation and/or breast implant size/type/profile will most likely help achieve your goals.
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as “natural” or "C or D cup" etc means different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on who makes the bra; therefore, discussing desired cup  size may also be inaccurate.  The use of computer imaging may be very helpful during this communication phase.
3.  Once you feel you have communicated your goals clearly,  allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals.  Again, in my practice, this decision is usually made during surgery.
I hope this, and the attached link ( dedicated to very active patients), helps.

Thank you for your question and photograph.  From your photograph you appear to be an excellent candidate for breast augmentation.Both sizes that you mentioned 330 cc or 3 75 cc should give you a full breast.The most important factor in avoiding the fake look is the quality of the surgery you'll receive.  An expert board certified plastic surgeon should be able to properly place your implants so that they will look appropriate.  It sounds as though your surgeon has chosen an appropriate size range.  As long as you do not form capsular contraction you should look natural.  Since you chosen under the breast textured is less likely to produce capsular contraction according to recent studies.