Hello from JustAnswer.
The first thing to do would be to rest for about 15 minutes to see if the blood pressure improves slightly. There is concern about a diastolic blood pressure (the lower number) over 110. If the pressure gets below 110 with 15 minutes of bedrest, then it would be OK to continue to try to address this at home. However, if the diastolic blood pressure remains above 110, it would be appropriate to be checked.
Within that context, it also would be appropriate to check to assure that you are getting accurate readings. In the vast majority of cases, someone with a systolic blood pressure of 142 will have a diastolic blood pressure that is lower than 110, and usually lower than 100. If you have an alternative method for checking blood pressure, that would be fine, or checking both arms to see of there is some improvement may offer reassurance that the diastolic blood pressure is not above the 110 threshold.
If the blood pressure is elevated, but not at a potentially dangerous level, and the pulse is in the 90s, then the usual next step would be to increase the dose of the metoprolol. You are still on a relatively low dose of the metoprolol, with a maximum dose of 450 mg per day of the regular pill (or 400 mg per day if you are switched to the sustained release formulation). So, the usual approach would be to gradually increase the dose of the metoprolol until either the blood pressure is controlled, the pulse is lowered to about 60, or the maximum dose is reached. The rate of increase can vary, and it sounds like you doctor is being cautious, probably because of the history of excessive lowering of blood pressure with the losartan, but adding another 25 mg pill per day would likely be the next step.
If I can provide any further information, please let me know.