Since you have been outside the US for less than 5 months, you should be able to return on OPT status. In addition due to cap-gap your OPT can be extended until your H1-B change of status (October 1st).
Check with your school's international office.
2.O. Can I reenter if I left while on OPT?
If your OPT has been approved and you depart before you get a job, your OPT ends and you cannot reenter unless you have a written job offer.
If you have a job, you may travel and reenter to resume work at the same job or you have a written offer for another job.
You should be able to return to the U.S. after traveling while on OPT as long as:
you have a valid EAD (OPT card)
you meet the immigration admission requirements for F-1 status (i.e. you have the required documents - passport, F-1 visa, I-20 and EAD, you are not inadmissible due to commission of a crime, etc, you do not have immigrant intent)
you have not been out of the U.S. for more than 5 months
you are coming back to resume employment
your I-20 was signed for travel within the last 6 months